My 4S seems very snappy since iOS 5.1 update. I will buy it just because it new. I don't need any other reason. They always have a good enough reason to buy. Plus, I always sell my old iPhone on CL for $400+ every year so why wouldn't I?
At this point I can't think of any reason why I wouldn't upgrade from my 4S. I always wanted a slightly larger screen, however, that is not an issue now that I have the New iPad.
I won't buy one if it is still the same form factor as the 4 and 4s. I like the curves of the earlier models. They really fit naturally into your hand.
Gotta say, unless Apple does something so remarkable with the iPhone 5 I doubt I will upgrade. I have zero issues with the 4S and I only go the 4S because of Siri. I would have stayed with the iPhone 4.
As for LTE I am in Albany Oregon, need I say more?
I would like to see a larger screen, heck that alone would be enough for me. 4" is the sweet spot, while I enjoyed my other android devices that had larger screens the iPhone 4S is so much more pocketable.
I wont buy the next iphone if it doesn't have a 4 inch screen.
( im on sprint and wont be getting even a drop of LTE for another year and a half. And thats not speculation thats in writing from spints roadmap of LTE.)