i use a treo. my partners use a blackberry. both are decent but if you plan to use a lot of email checkup, go with blackberry. if you like the bells and whistles and can accept the fact that the phone will crash a few times out of the week + going through buggy lag and load time, then get a treo. if you want reliability without needing to view videos and other multimedia shit, then get the blackberry.
my next phone will be a blackberry.