Computerworld recently conducted field testing of AT&T Wirelees' EDGE and UMTS networks. EDGE is available nationwide while UMTS is only live in six cities. Here are the speeds they saw overall:

ComputerWorld compared the UMTS speeds to DSL, which I would say is a stretch. I suspect the favorable UMTS speeds were in no small part due to the low uptake overall. And I would say the same thing about the high rates seen by early testers (myself included) of Verizon Wireless' EV-DO network. Still, EV-DO on a bad day is going to be faster that UMTS on an average day.

In the end, these numbers are just that, numbers. Everything hinges on what type of application you're trying to support. If all you're doing is basic Google searching (which consumes very little data), you should have a pleasant experience. Video streaming is going to be a bit more challenging.