Battery life: if you're really barely making it to the afternoon while only checking a few emails, there might be something running in the background. Is it warm? Double click home, then hold down an icon in the bottom row until it shakes, and starting hitting "-" to quit apps. You might want to reboot, too.
I'm a heavy user and bought a Lenmar battery case for my 4S. I ususally don't dip into the built-in battery until evening. Only $35 on Amazon, and very protective, too.
I do wish that instead of making it 20% thinner they would've given it a bigger battery. I think more people would appreciate that than would appreciate going from super thin to even thinner.