Cellphone advice?

[usernamenumber]

Sequoia and I's Cingular contract is about to expire. I haven't had any problems with them, but am considering using the opportunity to change as a way to leverage a better phone, better plan or something. I can probably do this while staying with Cingular, but I figure I might as well ask: does anyone have suggestions for providers I should consider-- or avoid, in the Boston area?