You have to make sure it will work on the TMO network. Also there will be no warranty coverage in the US and even paying Samsung US to repair it, won't happen.
Also some people that get international versions of Pines and use them here, will not get good service even though it is compatible. Sometimes the international phone won't use the best bands here.
You will get updates directly from Samsung, but that is something I don't worry about, even though I get timely updates from TMO. I never keep a phone long enough to worry about getting the update from Samsung or the carrier, I generally just buy the newer phone into the newer OS.