After two and a half years (or so) of existence, Apple's iOS App Store has hit the 10 billion downloads mark.

The 10 billionth download was made by UK resident Gail Davis from Orpington in Kent, who downloaded Paper Glider, a free game from UK company Neon Play.

This marks a huge milestone for Apple and the store front launched a few years ago to go along with Apple's iPhone SDK. Apple CEO Steve Jobs first publicly demonstrated the then-new App Store in March of 2008 along with the iPhone 2.0 software, calling it "an application we've written to deliver apps to the iPhone".

And deliver it did.

It took nine months to reach one billion downloads and a little over a year to hit two billion. All the while Apple collected a nice percentage of revenue from each app that was sold. Many developers made a pretty penny in the App Store, too.

However, not everything about the App Store is pretty. Everyone remembers the 2009 Google Voice debacle, in which Apple rejected Google's official app from showing up in the App Store. The move inspired the FCC to look into Apple's vague app approval process, which was frequently criticised.

Last September, Apple finally demystified the approval/rejection process by releasing App Store Review Guidelines. In November, the official Google Voice app finally made its way into Apple's store. It goes without saying that the App Store has been a huge success for Apple and its wide selection of apps is arguably one of the biggest things standing between the iPhone and its competitors.

But that may soon change.

The Android Market is gaining ground quickly. In December 2010, AndroLib reported that the Android Market had more than 200,000 apps. That report came just two months after Google announced it had 100,000 apps in its market. Daniel Ionescu from PC Advisor's sister title PC World projected that the Android Market could overtake Apple's iOS App Store by this spring if growth continues at the same rate. Something tells me that Apple isn't too worried about that. 

See also: Microsoft fights Apple trademark on 'App Store'