SunCom: I've had Suncom since I moved to VA and I cannot say enough good things about it. They actually answer your calls on either the first or the second ring (At least when I call) Also, in my area, I have almost perfect service, and not just near highways. The only dead zone I have found so far is in my room
. But I despise paying $2 for detailed billing, it just seems like too much money for the service.
Nextel: Well, everyone I know seems to like their Nextel, except for the Walkie-Talkie. As it seems, it is not entirely "free" and there can be many hidden charges associated w/ it. I don't have a Nextel, so I cannot elaborate.
Cingular: Is quite popular back East, and most people I know are satisfied w/ the level of service, although they have complained about the knowledge of the customr service reps.
One of the most important parts of choosing a Mobile Company is definetly LOCATION. Cingular and T-Mobile have poor reps down here, but my people in Boston have nothing but praise for them.
Also, be sure the plan you buy will suit your "talking needs". For most companies you can upgrade your plan w/o a penalty, but you cannot "downgrade" a plan w/ the same ease. So, if this is your first phone, you might want to try an entry-level plan and then upgrade if need be.