I've had a Treo 600, 650 and an early Blackberry (the model number escapes me); I'm firmly in the Treo camp. Blackberries are excellent e-mail devices, but the utterly suck as phones, IMHO.
The Treo 650 has turned out to be a good balance of it all for me; much better than the Blackberry, though I'm keeping an open mind on upcoming products...
