Apps that I use 99% of the time are CardioTrainer(running tracking with support for BT heart monitor), TweetCaster(The best twitter client bar none), Pandora and setCpu for overclocking with profiles setup for different battery levels.

Oh yeah, Im using it on HTC Evo with sprint and Google Voice integration is nothing short of amazing. I can pickup phone calls via my Gmail when Im on my laptop and I didnt have to change or port my phone number