Apple:

This update contains improvements and other bug fixes including: - Fixes bugs affecting battery life - Adds Multitasking Gestures for original iPad - Resolves bugs with Documents in the Cloud - Improves voice recognition for Australian users using dictation Macworld has more details. I've been running the Beta 1 and Beta 2 versions of this update for several weeks. All of the battery life issues folks have been experiencing on iOS 5 is fixed by this update. The difference is night & day. You can update using the old method of connecting to iTunes, or you use the new delta update method, over the air, by going to Settings -> General - Software Updates. This second method is what I recommend as it is much quicker and doesn't involve a long restore of your iPhone after the update finishes.