I once had an iPhone 3GS. Got it "factory unlocked", and put a T-Mobile SIM in it. It worked on T-Mobile, but service wasn't that great, I would often get "No Service available" in some places. I was told that was because the 3GS wasn't originally designed to work with T-Mobile's system (that's why T-Mobile wasn't one of the networks originally offered with the 3GS). It only processes half the T-Mobile signal, or something like that. Now comes the iPhone 5, which I'm told IS designed to work with T-Mobile. If I get one, I hope it will work as well with T-Mobile, as my ancient Nokia 6800 does. I assume the iPhone 5 that originally came as a T-Mobile phone, works pretty will with it. But my question is, If I get an iPhone 5 that originally had another carrier (like ATT etc.), and then it got "factory unlocked", will that one work as well with T-Mobile as an "original T-Mobile iPhone 5"? Anybody know? Thanx all!