freitasm: If you can unlock it, yes. Mind you, AT&T customises a lot of their handsets, so you will end up with apps that are only for their subscribers, or strange configuration options...
Has anyone ever unlocked an AT&T phone for use in NZ?
Normally I wouldn't bother, but for $550 NZD I can get an off-contract 920 with a charging plate and a monster headset. My guess is the headset and charger will probably retail for about $250 NZD, so it's a big saving... mainly I just want a different colour.