The reason I have is killing tasks like Camera, which appear to chew away at the battery even as they sit in the background... It wasn't until I started using a task manager that I started getting decent battery life out of my N1.

The first week, I followed the party line- I didn't touch a task manager. And the first week I was seeing 20% of my battery drained by 10 AM in the morning while using it for under 15 minutes since I pulled it off the charger.