Since upgrading my 4 to iOS 5, my phone seems to use more battery, quicker.

Before, I could go to bed with 100% charge, and wake up 8 hours later with it on 96-97%. Now it's around the 85%. Also, in the past 15 minutes, I've been web browsing and have used 5%.

Admittedly, it's not a major issue, and the iPhone's battery is infinitely better than my old HTC phone, but I'm just trying to put my finger on what is causing my battery to drain faster. Or am I just being paranoid?

Just went to 89% while writing this message...