I have the Blackberry Curve. The mobile web is decent enough to where I can check sosuave and even post without getting too annoyed. But the apps are what makes it even better. With apps for Facebook and Twitter its super easy to update on the go. The GPS and geocaching apps have also come in handy.
@Desert Fox, you don't neccesairly have to go with Sprint's everything plan. I have unlimited data, text, gps, and 450 minutes for 70 dollars. Plus, Sprint's evening minutes start at 7, not 9 like Verizon. Sprint is also pretty much the cheapest of the big three. (Sprint, Verizon, AT&T)