USB modem/phone for GPRS+EDGE ?

What hardware should I be looking for if I want a way to get my Linux
laptop online through the AT&T EDGE service we subscribe to? I'd prefer
not to have to touch any Windows software nor proprietary drivers at
all, and I'd be connecting through USB, not Bluetooth. If the 'modem' is
actually a cellphone, that's fine; I have a mild preference for cheaper
candybar-style phones, but overall I'm flexible. I'd prefer not to have
to fall back to GPRS-only.

I've found lots of spotty and out of date information by googling, and
some that assumes Bluetooth, but nothing particularly recent or
reassuring; I want to be more sure than 'probably' before buying. And,
plenty of phones seem to offer USB plus EDGE (e.g., the Motorola L7) but
it's terribly hard to find out if some playing with ppp over usb, etc.,
would actually let me get online through it.

Mark
.