I was upset with the 4S battery and figured it was really just a hardware issue(all iPhones have had 1430MaH battery) because the specs were getting too high... but iOS 5.1 has improved the battery a healthy 20%. I'm impressed as well.
EDIT: Can't believe I forgot the second 'o' in too.
Last night I went to bed at 10:30 and had 92% battery, woke up with 88%. That shows it's been improved, less than 1% drain an hour. Normally I'd wake up after 8 hours with a 10-12% drain, but this time it was only a 4% drain. And at work I noticed that it didn't drain much at all when the phone was left idle.
Well of course you will get stats like that when you plug your phone in to juice it back up. I call bs on this. Try getting those stats without plugging it in.
