Yes.... everything will work (even 3G) as long as the network you are using supports it and your sim card allows the use of data.
Things like picture messaging and visual voice mail are also contract and network dependent.
Otherwise, everything else should work.
(I understand that only AT&T have 3G in the States but the phone will work using Edge on Verizon, for example).
Edit: I've been told its T-Mobile not Verizon that uses Edge, and Verizon won't work at all.