Google+ launched the Android app, G+, before it launched the iPhone app, yet the iPhone G+ app has quickly jumped to the top of Apple's Free Apps list.

Facebook still holds the title for the most downloaded app for the App Store to date, due to its 750-million user base. It still remains to be seen if Google+ can compete with or surpass Facebook as a social media platform.

According to estimates, Google+'s user base has tripled from last week's mere five million to 18 million by Tuesday. And considering Google+ is currently in invite-only mode, it's an impressive feat that the iPhone app has jumped to the top so quickly.

When Google+ announced the launch of the G+ iPhone app, there was an unprecedented excitement hitting the social media waves via Twitter.

However, despite launching the Android app the same day that Google+ launched, Android users don't seem to be taking to G+ as quickly as iPhone users. Facebook for Android is currently the second most-downloaded free app on the Android Market, following Google Maps at the number one spot. Google+ comes in at eighth place following Angry Bird, Pandora, YouTube and others.

What slightly differentiates G+ from Facebook mobile is that rather than grouping your friends together using Friend group names the way Facebook does, G+ uses Circles. These Circles allow users to have a more exclusive sharing platform -- sharing just the right information with the right people.

G+ also has Stream, which act like a Facebook Status. But, what G+ has that Facebook apps don't currently have is the Huddle feature, which allows fast group messaging for those in your circles.

However, despite Wednesday's excitement over the G+ iPhone app, there has been disappointment too. Many users were complaining about the app being too slow, and are frustrated that IOS5 is unsupported, for now.

Punit Soni, who helped develop the iPhone app responded on Tuesday via Google+. Some of the issues he addressed go as follows:

1. It doesn't keep me logged in. Even though I had told it to. Oh, wait, now it is.
Soni: We have not seen this issue so far. But we are going to do another round of testing on Authentication and iterate.

2. I don't see a way to upload a photo, like the Android app has. Never mind, I found that, you have to click on the photos app where the camera icon is very small.
Soni: Thanks for the feedback. We will take another look at our UI flows.

3. It frequently freezes on me.
Soni: We discovered an issue where the App freezes when there are posts with tons of comments on it. We have a fix for it and it's coming soon.

4. It has crashed twice so far. UPDATE: Six times.
Soni: This may be related to the lack of IOS5 support. We are digging deep into other crash reports as we speak.

5. No way to share.
Soni: That is a feature we are working on for both Android and iPhone. Coming soon.

And the complaints don't stop with iPhone users. One blogger posted in a forum a concern over the Android G+ Photos Feature stating, Every day I post a pic to G+ it creates a completely new sub-album under the Photos From Posts album. To make matters worse, if I post photos to more than one circle/privacy-condition, I will have multiple albums for the same day.

As a result, I now have to scroll through a crap-ton of albums in the Gallery app. And if I decide to share/upload a pic straight to Picasa, I have to scroll through an obscene amount of folders in the Picasa uploaded just to tell it which folder to upload to.

It hasn't even been 2 weeks yet and it's getting to be a problem, and I can imagine how much worse it will get only a month from now.

There has also been some criticism over the amount of users Google+ was able to achieve in its first three weeks, compared to its main rival, Facebook. One thing to consider is that Google+ reached a certain, chosen capacity and is currently allowing new users to sign up by invitation only.

Paul Allen, who gave himself the title Google+ unofficial statistician, who also founded Ancestry.com, posted on Google+ that the total user base jumped to 18 million after more than 750,000 peopled joined on Monday alone.