I'd stick with either a Treo or Blackberry, but that's just my opinion. I've always liked Treos the best - probably what I'll upgrade to this summer.
All I have heard about the treos is negative from 3 different at&t stores. They say that the OS is very poor and if freezes up often, and some of the claimed features will stop working. Granted, it is covered under warranty, but how often do you want to have issues? That is why I am not even considering them.