Yes, another 4/4S question. I am on T-Mobile and recently (within the 14-day return period) bought a factory unlocked iPhone 4 (black). It is working beautifully and is a great phone (I had an iPhone 4 on AT&T a few years ago but have since switched to T-Mobile). I do not have or want a data plan, since mostly everything that I do is within wifi range. Anyway my question is what kind of advantage (if any) would I see if I returned the 4 for a 4S? I am thinking not much if any (I think that Siri would be useless w/o a data plan, correct?), except for 16GB instead of 8GB storage space. I don't know if the faster processor would be noticeable or not since I have not used one. I guess my main purpose for exchanging if I do would be future resale value. If I were to upgrade to the iPhone 5 when it comes out I know that a 4S would bring more than a 4, but how much more? Would it be more than the $100 premium I would be paying to exchange? I just want to cover all of my bases. I have also toyed with the idea of returning mine for a white model, but I know that is simply personal preference.