Apple's latest mobile operating system iOS 5 promised deep Twitter integration among its 200-plus new features, by allowing users to tweet directly from Safari, YouTube, Maps, Camera, or Photos, and even add Twitter usernames to contacts for easy replies and mentions. Since the free iOS 5 upgrade became available Oct. 12, Twitter has seen sign-up rates via iOS devices such as the iPhone, iPad and iPod Touch more than triple.

The iOS integration is going to be absolutely huge for us, said Twitter CEO Dick Costolo at the Web 2.0 Summit in San Francisco Monday. It's going to be even better than we thought it would be.

Sign into your Twitter account once in the device's settings, and you'll always be connected. Besides being able to tweet from Apple's apps, users can also tweet directly from third-party apps such as Instagram, Flipboard, LivingSocial and Zynga's Words with Friends.

Costolo says Twitter has racked up more than 100 million global active users, but even more impressive, more than 50 percent of those users log in daily. This is an astounding jump from the beginning of the year, when only 30 percent of monthly active users logged in daily.

Twitter processes more than 250 million daily tweets, and its mobile platform is growing roughly 40 percent quarter on quarter. Thanks to its early success on iOS 5, Twitter hopes to do more mobile work with Apple in the future.

Those guys [at Apple] are an amazing partner for us, Costolo said. When they think about products and enhancing products they think about editing them. [At Twitter] we're going to offer simplicity in a world of complexity... they're a corporate mentor to us.

This is a big boon for Twitter, which has always trailed Facebook in size and popularity. By working with Apple, Twitter has the chance to become more mainstream and emerge as a true alternative to Palo Alto, Calif.-based Facebook.

More users may join Twitter after Facebook's latest changes, which have consumers in an uproar yet again. Facebook's new Timeline profiles, which were unveiled at the f8 Conference on Sept. 22, have been bashed by users. A telephone survey of 2,000 people conducted by Gallup and USA TODAY discovered that 56 percent of Facebook users who know about the changes to the social network dislike them, and 26 percent of people who use the site daily are very concerned about privacy.

This aligns with an earlier study, which noted that about 59 percent of users said they couldn't be bothered to fill in their Timelines. Twitter's decision to be simplicity in a world of complexity may sound much more appealing to those users who feel Facebook is overstepping its boundaries.

We have been and continue to be very focused on that simplified experience of Twitter, said Michael Abbott, the company's engineering VP. I think that's one of the reasons we've seen the growth. People get it, so people use it.

Twitter will try to retain its simple appeal while also finding new ways to deepen engagement with its user base.

We need to be able to surface content so people coming for the first time discover what's happening in their world and in the world, Costolo said. To separate the signal from the noise.

Costolo hopes to add richer content, more promoted tweets and more ads in an effort to help businesses amplify the communications they're already having on Twitter.

Now the headlines will be: 'Costolo: Movie ads coming to Twitter,' he said. That won't happen. Twitter will introduce ads that resonate with what Twitter users are used to.

Twitter, which was launched in July 2006 by Jack Dorsey, Noah Glass, Evan Williams and Biz Stone in San Francisco, has earned an $8 billion valuation since raising more than $800 million in August.

We have lofty ambitions, Costolo said. We want to be part of the fabric over every communication in the world, and we think we can reach every person on the planet.

With Apple's help, Twitter may reach that goal very soon.