Here's an interesting set of charts from Nielsen analyzing the most popular apps on each smartphone platform.
As you can see, app usage is pretty uniform across the board. Smartphone users love Facebook, Maps, Pandora and the Weather Channel.
There's only one really glaring exception across the platforms. Apple's iPod and iTunes are huge on the iPhone. On BlackBerry and Android, music players aren't very hot.
This explains Google's purchase of Simplify Media to build a better music player and music experience for Android.