Owners of iPhones and iPads are anxiously awaiting the release of iOS 6, the sixth-generation operating system for Apple's line-up of mobile devices, coming this fall. Though Apple hasn't specified the release date of iOS 6 -- the official site currently says it's "coming this fall" -- many believe Apple will release the platform alongside a new iPhone and possibly a new "mini iPad," which are both expected to be unveiled and released in mid-September.

The iOS 6 system looks to be right on track for a September release date, as Apple released the fourth beta build of iOS 6 to developers, also known as Build 10A5376e, on Monday morning. The newest beta comes just three weeks after the previous developer version of iOS 6, Build 10A5355d.

Apple has been known to release as many as six or seven beta builds before the golden master, which in hardware and software terms is essentially the finished product, or the mold from which all other copies are mass-produced. Apple would need to release the golden master of iOS 6 by the end of this month or beginning of September in order to ship the software out to new iOS devices being built (reportedly, the iPhone 5 and iPad Mini). At that point, shipping the devices could take an extra 10 to 12 days, which would peg the official release date around mid-September.

Unveiled at Apple's Worldwide Developers Conference in June, iOS 6 adds 200 features to the mobile platform, making it one of the most comprehensive updates Apple has ever released unto its mobile devices.

The predecessor to iOS 6, iOS 5 introduced several key features to the mobile platform last year, including an organized Notification Center, deep integration with Twitter, a free messaging service for iOS users called iMessage, and a cloud platform for storing and streaming documents and media files to any iOS device, called iCloud.

In iOS 6, Apple is introducing a new Maps application made in-house (sorry, Google), deep integration with Facebook, and a number of significant enhancements to Siri, the virtual personal assistant currently exclusive to the iPhone 4S. Siri can currently place calls and texts, set alarm reminders, play music, surf the Web, get directions and answer questions. In iOS 6, Siri will know everything there is to know about past, present and future sporting events and movies, and it will also be able to launch applications and give turn-by-turn navigation. Also, in iOS 6, Siri will be available on the latest-generation of iPads.

There are more than 200 new features coming to iOS 6. Here's what you can expect this fall:

Maps: Apple introduced a new Maps application as a part of the iOS 6 platform coming in the fall. But this Maps app isn't built by Google; this one is Apple-made. Apple's Maps application includes new vector-based 2D map elements, 3D maps, detailed traffic conditions, and best of all, turn-by-turn navigation with a dynamic 3D camera perspective. The entire platform is completely compatible with Siri, which will give you directions even if your iPhone oriPad is locked.

Siri: The AI virtual assistant was born on the iPhone 4S, but with iOS 6, it's finally making its way to the new iPad, too. Since the feature was first released in October, Siri, which could help users place calls, create and send texts and e-mails, set reminders and schedule meetings, surf the Web, or answer complicated or context-sensitive questions, has gotten only smarter. In iOS 6, Apple has endowed Siri with encyclopedic knowledge of sports (current, past and future), movies (current, past and future), and even businesses and available restaurants. Users can also launch applications with their voices, and Siri can also help the user post a message to Twitter or Facebook, just by speaking.

Facebook Integration: In iOS 5, Apple elected to optimize nearly every app for Twitter, which allowed users to tweet photos, webpages from Safari, videos from YouTube or even their location, for all of their Twitter followers to see. In iOS 6, Apple decided to apply these same tactics of deep integration with Facebook, the world's largest social network with more than 900 million users. This fall, users only need to sign into their account once to be able to share content -- text, links and photos -- onto their Walls or each others' Walls, seamlessly sync their Address Book Contacts with their profile photos from Facebook, and receive notifications over the Notification Center. In return, Facebook added its Like Buttons to the App Store and iTunes Store, and it now syncs its Events with Apple's iOS Calendar.

Accessibility: The relationship between Apple and its users is very close, but Apple has gone out of its way to make the mobile experience friendly with students and children with hearing, vision, learning and mobility disabilities. Apple has added several features that help students remain on task and focused on their content, giving teachers, parents and administrators the ability to limit the device's abilities and disable certain areas so the child only touches what you want them to touch. With integration into Maps, Zoom, and AssistiveTouch, Apple is looking to help blind or low-vision users, and the company is also looking for hearing aid solutions to give its users a quality audio experience.

Features From OS X "Mountain Lion": In an effort to better merge iOS with the Mac operating system, Apple added several features from OS 10.8 Mountain Lion to iOS 6. Apple added Mail VIPs, a "Do Not Disturb" feature for the Notification Center, and a new feature called iCloud Tabs, which lets users view their tabs opened in Safari across all iOS and Mac devices. Users simply click a designated iCloud Tabs button and all the tabs opened on each device are shown in a synchronized list, letting them see what's open across all their Apple devices.

Phone Features: Apple hadn't touched the general Phone feature since it was introduced in 2007 with the first iPhone. In iOS 6, Apple has created more options for users to deal with incoming calls, including options to reply with a quick message, or a reminder to be set for a certain time or a certain place. For video-chatting, Apple also added FaceTime support over cellular channels, including 3G.

Passbook: As mentioned, iOS 6's "Passbook" keeps digital tickets, coupons, loyalty cards and gift cards organized in a simple location. Clearly this is the precursor to the NFC-based "iWallet" technology, which will similarly keep your credit and debit cards in a safe and secure location for easy access.

Custom e-mail alerts: Apple added a new VIP mailbox so users can put all messages from their most important contacts in one place, but in iOS 6, Apple also made it easy to alert yourself when those users send you new messages. iOS 6 includes custom e-mail alerts for accounts (VIP mailbox vs. inbox) and for people (mom and dad vs. that random PR guy who won't stop e-mailing you). In addition, this setting also works with the new "Do Not Disturb" feature, so you can silently receive incoming e-mails without disturbing your slumber, a meeting, or anything else you may be doing.

Clock for iPad: The iPhone always had a clock app, but Apple left out the app in the iPad, for some reason. Well, no matter, Apple is fixing that in iOS 6. The new mobile operating system will endow the iPad with a new Clock app, complete with features like alarms, timers, and the ability to see the time in different places around the world. But the biggest reason why Apple avoided creating an iPad Clock app -- the difficulty of making it look good on a big screen -- is certainly present here. Each actual page on the app looks like a separate app entirely, and some of the features, including the stopwatch feature, look pretty hideous. Luckily, the most important feature -- Alarms -- is pretty nifty. Users can set their alarms, but also flip the screen to see their alarms all laid out on a planning calendar. The iPad Clock can also let the user choose any song from their iTunes Library to create as their alarm, which should put many third-party clock apps out of business.

Reminders Badges: The Reminders app, introduced in iOS 5, was supposed to help users keep track of their outstanding to-dos. Unfortunately, if you're just browsing through your iPhone, you can't see all of the tasks you haven't completed yet from a distance. That will change in iOS 6: Apple has endowed its Reminders app with badges, so anytime you still have a reminder to take care of, you'll see the app icon with a number circled in red on the top right corner. That number signifies how many reminders are remaining, which should be better for keeping users on-task.

Find My Friends Optimized: Apple introduced a slightly creepy but ultimately useful feature in iOS 5 called "Find My Friends," which let users search and discover their iOS-owning friends on a map. In iOS 6, users can opt to receive alerts when a friend enters or leaves a certain location, which Apple calls "geofencing." In other words, if you're a worried father about his daughter's first trip to New York City for an interview, you can set up an alert to tell you when your daughter arrives in the city, and you can also alert yourself when she leaves the city, or arrives at the train station nearby. It's extremely useful for anytime people need to coordinate meet-ups, or if parents need to check on their kids' statuses when traveling.

Bluetooth Enhancements: Bluetooth 4.0, a.k.a. "Smart Bluetooth," can create near-instantaneous connections with other devices. In iOS 6, which includes this latest version of Bluetooth, Apple is making this connectivity option much more accessible. Now, users can turn Bluetooth on or off right below the Wi-Fi option in the Preferences app, which should help some users cut down on battery drainage by limiting what connections their device is making. This feature was heavily-requested, and Apple listened.

Updating Apps: One semi-annoying feature in iOS 5 is how Apple requires users enter their Apple ID passwords just to update their old applications or download prepurchased apps from iCloud. Luckily, this minor annoyance will be done away with in iOS 6. For prepurchased content and application updates, Apple won't require users enter their password. Furthermore, when a user buys or downloads an app from the App Store, they won't automatically be kicked to the home screen to watch that app download, letting the user continue to shop to their heart's content.

"New" Banners: Users can download so many apps from the App Store that it becomes difficult to keep track of where all of the new applications are. Luckily, Apple has added a simple feature in iOS 6 that places a blue ribbon around your newly downloaded apps with a "New" label, just so you can find it.

Dictionaries in the Cloud: Even though there are applications for the dictionary and thesaurus, Apple decided to make it easier to reference the dictionary in iCloud. Apple decided to add a full personal dictionary in iCloud, as well as French, German and Spanish dictionaries for the out-of-town folk. 

Color-Matching Menu Bar: Apple loves throwing in super cool, super small features that only the biggest fans would appreciate. This one is no different: In iOS 6, Apple has made it so the menu bar changes color depending on what's going on in the background. Apple has done this for when you receive a phone call -- the menu bar turns green -- or when you become a personal hotspot -- it turns blue -- but Apple has gone a little wild in finding new configurations for having its system complement the app. For instance, when you open Facebook Messenger, eBay, or an Adsense app called myRevenue, you can see a different paint job on each of the menus. It's not clear to what degree Apple will open this option up for developers, but it's certainly a brilliant design move that shows Apple's close attention to detail.

Faux Light Reflection: If you thought the last feature was persnickety, this feature may seem downright absurd. Even though this feature is 100 percent useless, it is a brilliant design feature nonetheless. Nobody really pays attention to the metallic volume slider within the iPod application, but Apple has made a subtle change where the slider actually changes its reflection based on how the iPhone or iPad is tilted, as if the metallic button were actually reflecting light. Again, it's just another example of Apple's intense attention to detail.

Which features in iOS 6 are you most excited for? Do you typically download the new version of iOS as soon as it's released? Will you download iOS 6 when it comes out? Let us know your thoughts in the comments section below.