If you sync with an exchange server, and you've got push mail on it, then look at the wm smartphone devices like the Motorola Q9, or the HTC Excalibur. You'll get excellent syncing, a cr4p browser, gmail over pop3, and an mp3 player for if you ever discover them

I used to run an O2 XDA2 then HTC Tytn until I discovered the n800. The Tytn is a fantastic device for mail, and the Q9 is nice for mail/sms purposes.

The big advantage over the blackberry's is that you don't have to subscribe to their over-priced services, on top of your regular line rental.