SmartPhone OS thoughts?

[alexxkay]

My current phone is getting battered enough that I am thinking about replacing it. I've been a Palm OS user for many years, but Palm OS is going away soon, so it seems like I should probably figure out what OS I'm moving to next. The major contenders seem to be Windows Mobile, Android, Blackberry, and WebOS. (A keyboard is an absolute must, which is why no iPhone.) Anyone out there want to evangelize (or demonize) any of these?