I made the jump from a 4S to a GSIII and to the iPhone 5.
I have to say, after a few days of use, I don't even miss the big screen on the GSIII, but appreciate the bump from the 4S. The iPhone 5 is a great piece of hardware.
There's a lot I miss from Android, but to be honest, iOS is so much more fluid. With the release of Google Maps last night, I am a happy, happy camper.
Only had the iPhone 5 for about a week, but it's been great so far. Battery usage is much better than the GSIII. I can go a full day without worry, and still have enough left over to leave it unplugged over night (IE if I forget to plug in).