A little background information before I get into the iPhone 4S battery life. I had an iPhone 3GS from day one some odd 2.5 years ago. I watched the Apple presentation on the 7th, had a temper tantrum, and purchased a Samsung Galaxy SII that day for a myriad of reasons. It was actually a very fine phone, just not an iPhone, which it took me about a week to figure out. I take the Galaxy SII back and was able to pick up a new 4S yesterday. Here I am at 12:27pm, and my battery life is at 84%, with some pretty heavy Facebook/Twitter/Email usage throughout the morning. I can tell you right now that my Galaxy SII would be around 60-65% right now with the same amount of usage. That was one of several reasons why I took the Galaxy SII back, was because I was almost afraid to use the darn thing given how quickly the battery went. I'm sure the 4S probably doesn't have any better battery life than the 4, but keep in mind that I'm coming from a 2.5 year old 3GS and a Galaxy SII. To me, the battery life on the 4S is amazing! YMMV.