[jedbrown]

If you want 3G in the US, then your choice of phone ties you to a carrier. I own a Vibrant (off contract) and although I can use it with any carrier when in Europe, I couldn't leave T-mobile because the 3G radio won't work with other US carriers. (I'm happy with T-mo, but that's not the point.)

[jmillikin]

I have an unlocked Vibrant, and it works well on AT&T's 3G network. Generally it's AT&T phones that don't work well with others, since they actually disable non-AT&T frequency bands.

[jedbrown]

Interesting, all the specs I've seen say it only supports UMTS Band I (2100, Europe) and IV (1700 "AWS", US T-mobile). You'd think they would have mentioned that it also supports band II (1900, AT&T). I just ran a fresh search and came up with this page which supports your claim, but it's absurd not to list it anywhere else: http://ars.samsung.com/customer/usa/jsp/faqs/faqs_view_us.js...