These devices were not around when I was in college, as Nextel had not released them, and T-Mobile was servicing my area. They moved into my market at the same time that they finalized the buyout by D-T and changed their namee from VStream to T-Mobile. Bear in mind though, I am only 22, and could still be in college, so this thread applies to me.
I first got into data devices with a Sidekick CS about a year ago. Got rid of it due to size, then about six months later, got an SK II, switched from T-Mo to Cingular, got a BB 7290 for voice and SMS about 3 months ago, then just switched back to T-Mobile with a 7105t. I have $45 for voice, and $20 for unlimited data, BIS BB, SMS, and IM.
I left school after a year and a half to take a break, got a job in IT, went back to school for another semester, then got a new job which has me on the road all the time, and I have been with them for a year and a half. My BB downloads my mail from my company's OWA server, as well as Comcast web mail.
T-Mobile has the best BIS implementation in my opinion, and is fairly comparable to at least the e-mail portion of BES as mail sent from my BB shows up in Outlook when I get back to the hotel.