And that's not a negative. The 3GS was a huge upgrade to the iPhone 3G.
Not really. It was great to get more processing power out of the phone, but it wasn't as huge as the jump from EDGE to 3G or from the 3G/3GS form factor to the 4 form factor w/ front facing camera.
I know the iPhone 5 will sell just because it's the iPhone 5, but I seriously question the wisdom of anyone locking themselves into a 2 year service agreement with LTE/4G almost certain to be added to the iPhone platform in the 6 revision next year.
You can never truly "future proof" yourself, but it'd be silly to spend a lot of money and sign a contract for the right to own the last phone of the old cell data tech.