apparently you missed this thread:
http://www.dansdeals.com/forums/index.php?topic=57.0But basically, no, not really. Blackberrys, like all push-data centric devices, require a third party server to push data along a propietary protocol. In plain english, the blackberry needs a Blackberry Server to give you all the great stuff that makes a Blackberry worth having (push email, etc). You can "trick" AT&T into giving you a plain old data plan rather easily, but you won't get BB email without paying a monthly fee to rent server space. If I am not mistaken, you can however get it to work with pop3 or imap set to check on intervals like any other standard phone (even a moto RAZR can do that), however you won't be getting the BB email experience.
In my opinion, without the BB server, a Blackberry is just an expensive texting phone. I recommend you either pay for a BB plan or get a device that doesn't need one (windows mobile, Palm, Nokia S60, etc), plenty of which are available on AT&T.
(If you like the BB style, I recommend a Nokia E71- very capable phone, simple to use, VERY SLEEK, and does all the stuff a BB does but doesn't need a proprietary server to do so. If you want more raw power, check out the Fuze).