The thinness of the 5 does feel nice, but I'm always welcome to battery improvements. However, apparently the iphone 5 battery lasts longer than the 4S, so maybe we get the better of both worlds (don't have ip5 yet though, so can't test myself).
I always say that the phone is thin enough already. Then I get my hands on the new one and it's so much nicer to hold in your hand. It doesn't feel too thin. It doesn't feel too light. It's just right. I really like the design of the iPhone 5.
my iphone 5 battery life is much much better then my 4S. I had a mophie juice pack plus on my 4S. i would have to turn the juicepack on around 4pm. and it would still be down to like 40% again by midnight. yesterday I unplugged the 5 around 11am and by the time i was headed home at like 1230am and it was down to 6% on just the 1 charge. I use my phone ALOT too.
I replaced the battery in my iPhone 4 about 6 weeks ago, it crushes my new iPhone 5. Same usage, no LTE, and the iPhone 5 barely lasts half a day compared to my 4 that will go all day.
Might buy a mophie when they come out.
I wouldn't mind it staying the same thickness for a bit more battery heft. Not that the battery doesn't last long enough, I charge my phone every night as it is. However, I have had nights where I played a game or something else, and it pushed me into the red before I expected. A little extra life would be nice some times.