I'm still debating. I have a launch day 64GB 4S on AT&T that could probably still pass for brand new. No signs of wear because I keep it in my mophie juice pack plus, which is secure and made of hard rubber.
No, AT&T won't extend me an upgrade. They point to their strict agreement with Apple as the reason why. They won't even offer me any type of credit toward my bill. Called 3 different times and spoke to 3 different CSR's and each told me "Nothing we can do" in their own individual way. Not that I was expecting an early upgrade, but I figured it wouldn't hurt to try. I'd have to pay the $449 price for 16GB.
Now I COULD sell my 4S and get $350 for it, and, at the end of the day, break even. But, in thinking about it, I'm not sure it's worth it, coming from a 4S. If I had the 4, there'd be no question, but, functionality-wise, I'm hard pressed to find much that a 5 can do, which a 4S cannot....provided I get on iOS 6.
I won't have the bigger screen or LTE, but, truth be told, AT&T doesn't yet offer LTE coverage where I live. So, even with an iPhone 5, I would only get the same HSPA+ "4G" speeds which I already achieve on my 4S (which is actually fast enough for me).
The differences in speed between the 2 devices MIGHT be noticeable IF I did a side-by-side comparison. But again, we're talking differences in mere seconds at best. I don't do anything on my 4S that even makes full use of the A5 processor at the moment.
Truth be told...I bought the original iPhone in early 2008, but passed on the 3G. I held onto my original for 1.5 years and then got the 3GS in June 2009. Then, even though I had an early upgrade available, I passed on the 4, back in 2010, due to not liking the design and antenna-gate. I updated my 3GS to iOS 4 (at the time) and was all good. I sat on upgrade eligibility for well over a year, and then got the 4S on launch day. The jump from 3GS to 4S was quite large, and I was happy that I'd waited.
So, again, I think I shall keep my 4S through the duration of my contract, and then see what Apple has in store next year (5S, anyone?). If I update to iOS 6 - still on the fence about that too - then all I'll be short is the A6, HD facetime, and 4" screen...oh yeah, and the whole "lightning" thing.