Terripin, I live in Arkansas, I'm a T-Mobile customer and, here, I NEVER get EDGE service unless I'm browsing on AT&T. I've not read up on the what your are and are not suppolsed to be able to do but I'm an expert on what can be done with GPRS-only service. You CAN use it for data - it's slow as molasses but you CAN do it - I just turned off my wi-fi and did it again. You can also get emails and, of course voice service. As far as emails go, I don't really understand it but I sometimes get emails when I'm in a no service area - "SOS" - and can neither get nor place a call. Go figure that one out.
As far as the going to the coverage map on T-Mobile, it's not that accurate either. On their map my house shows the weakest service but I'm full bars as far the the signal strength goes. Conversely, when I go to my home town in E. Texas which shows to be one of their strongest signal area I get A LOT of SOS there.
Why to I continue to do T-Mobile. It's cheap and the wi-fi is great!