I mentioned in my initial iOS5 Beta impressions post that battery life seemed to take a bit of a hit with the latest beta. The day after the post, I decided to give the battery life a real world test. I was able to fully drain the battery in a 12 hour period under normal use. On iOS4; my definition of "normal use" would get me thorough a 16 hour cycle with around 35%-40% battery life remaining. Only making it 12 hours on iOS5 before my battery was completely drained would not be acceptable.
I found that turning off Location Services (Settings>General>Location Servies) for Weather and Reminders (and whatever else you don't need activated) appears to drastically increase battery life on iOS5. I was able to go through a 16 hour day with roughly 25% of my battery life remaining. While this is 10% lower then on iOS4, I consider it acceptable due to the new feature set and considering this is still a beta release.
In order to maximize iOS5 battery life during beta, I would also recommend completely disabling iCloud if it's not being used.