If we believe Google's statistics, then more than 1 billion apps are now downloaded every month, which indicates a strong growth rate given an average of 667 million downloads for the past six months. The first billion of app downloads was announced in July 2010, 22 months after the launch of Android Market.
Google is celebrating the milestone with ten 10 cent downloads every day - for the next ten days. Today, for example, Google is offering Asphalt 6 HD, Color & Draw for Kids, Endomondo Sports Tracker Pro, Fieldrunners HD, Great Little War Game, Minecraft, Paper Camera, Sketchbook Mobile, Soundhound Infinity and Swiftkey X.
In comparison, Apple announced back in July that its AppStore had passed more than 15 billion downloads. According to App Brain, there are currently 338,255 apps available in Android Market. Apple's App Store has 522,857 active apps, according to 148Apps.