I've seen a lot of indignation recently about the iPhone 4S battery performance. From my usage, I'm willing to bet the majority of people concerned are actually just misinformed by the battery cartoon at the top of the screen.
Today at 3pm I was alerted by my iPhone that I only had 20% battery left! I listened to an audio book on my drive home (about an hour). I then received a dire alert that I only had 10% battery left!
I subsequently listened to 2 podcasts over a BlueTooth speaker, took some photos of my daughter, spoke on the phone for about 5 minutes, sent a text message, added grocery items to my shopping list with Siri, did a couple web searches with Siri and checked email several times. It is now 9pm and the phone is still not dead.
Your mileage may vary, but for me, that last 10% of the battery is like magic.