I sold my 4 and bought a 4S.

It definitely feels "snappier" (to use that well known mac performance metric) although how much of that is down to the fact that I was without my 4 for a week.

Siri is pretty good, I was actually pleasantly surprised given how dire "voice control" was ("What time is it?"......"Calling Sarah...Mobile"). I had a chip in the screen of my iPhone 4 which was irritating, it was "just" over the display and because I knew it was there, my eyes were always drawn to it.

I'd have ended up paying £140 for a replacement, so I figured I may as well sell the phone on and upgrade to the 4S.

Haven't played with the camera yet. The smaller "shift" key on the keyboard due to the voice functionality requires a bit of operator retraining to hit the right key.

Biggest gripe is that the siri localisation changes both the voice recognition and voice, it'd be nice to be able to select the female US voice because it's much nicer than the UK voice, which just makes me think I'm listening to something from xtra-normal.