To be honest, I've never thought about it. It shouldn't be locked to a particular region, since we use the same protocols, but some ISP's do tend to lock their routers, so that it can only by used by them, and you don't go selling it on e-bay!
Normally, updating the firmware will overwrite any locks put on by ISP's, but updating any kind of firmware is a risky process. If anything goes wrong during the update, you won't have a second chance to try it again!
http://kbserver.netgear.com/release_notes/d102855.asp