I kept seeing all this talk of amazing battery life with UD and wondered why I wasn't seeing it on my D1. Turns out it had everything to do with DoubleTwist. Over the last week it had been acting strangely, turning on at random when I was using the stock music player, so I decided to dump it.
I unplugged my phone at 6:30am, and now here I sit at 3:00pm with 90% battery left after playing music for an hour on my way to work,taking 2 phone calls, and playing a game on lunch break (for about 10 mins).
So if your battery life isn't great and you have doubletwist installed, getting rid of it may be something to think about.