I had Nextel and hated it.. I never had reception anywhere which really sucked.. so i didn't really get much use of it.
I also had Sprint.. which none of my friends or family members had so a waste of my minutes.. reception is great, but i wasn't happy with the plans..
My boyfriend has Cingular and there isn't much of a complaint only no service once in a while..
I have Verizon and i freakin love it. I think they have the coolest phones. Plus all my friends have it so that means free mobile to mobile, free text.. and vcast! i love it..