I can only speak from my experience, but you are pretty much limited to devices as dictated by your cellular provider. As an ATT user, I have used Palm 650, Nokia E62 and now a Tilt (HTC Kaiser).
well you have a wide range of phone that will allow you to use blackberry connect data on them nokia makes a few sony makes a few and most windows pocket pc phones. its all about what are you looking for and what OS would you like to use.
MY Collection:--Nokia:E90 9500 9300 9290 N91 Sony Ericasson-P990I BLACKBERRY-9500 9000 8700 8300 8800 HTC-8525 THC Fuze