I had a 7280 for a year. I loved it for the e-mail and the keyboard. I tried a Treo 650 a couple months ago, and liked it, but it had multiple issues (mostly with POP3 e-mail and the fact that it doesn't work with Hotmail). I returned the Treo after a week and replaced it with a Blackberry 7100 series ("g" model, through Cingular).
The 7100 is okay, but I really miss the keyboard on the 7200 series. The screen is nicer; I like the form factor better than the calculator-like 7280; the holster for the 7100 provides much better protection than the 7280's hard holster (and it's much less likely you'll knock a 7100 out of the holster than the 7200 series...). The 7100 also has Bluetooth (not sure about the 7250), and better ringtones.
...but my biggest complaint about the Blackberry, versus the Treo 650 or even the Sony Ericsson I had three years ago, is that you can't use it as a modem for your computer...at least not with any ease. With the latest Blackberry desktop software and some tricky dial-up configuration you can apparently make it work, but there is still some question about the billing (is it included in the "unlimited data plan"?); and it requires some very specific billing codes to be set up on your account before it works. I have the instructions, but have not yet tried to make it work.
If the Treo 650 had the EM capability of the Blackberry (it's all in the email client software they use), then I would have kept that one...