T-Mobile is mighty fine in Ohio and most of Maryland. The only area I've had problems with in Tampa is around this hotel, but I think that be more because of its proximity to the airport. I get decent reception even in the Nielsen building.
Well, my friend's old piece of shit that's like, 5 years old now, and running on Bell can get reception damn near anywhere. Even int he middle of the school, with tons of concrete and metal all around. He gets something like, 3-4 out of 7 bars in my basement.
CDMA phones can transmit at a lower frequency -- 800MHz -- which offers better building penetration than many newer phones (which use a 1.9GHz band) and GSM phones (which, in all but rare cases, have a 850MHz floor). This is why older CDMA phones can, in some cases, get better reception at the expense of audio quality.
Like I said earlier, GSM also isn't as widely supported in the US and Canada. CDMA basically came first and GSM is playing catch-up. It's not that T-Mobile, AT&T, and Rogers suck, they just haven't been in this continent as long. I'll gladly take the freedom that GSM provides rather than having extra coverage and an overly-locked phone. Besides, if worst comes to worst, my company phone is going to be through Sprint, so I'll have the best of both worlds. :>