smib
is a big honkin' homo
Task killers don't help battery life, they actually diminish it. Android has good process management and shuts down apps and services when they aren't needed anymore, until then they just idle in memory. If you use a task killer to kill apps, you'll most of the time break a process in progress, which the app will have to restart when you start it again, meaning it'll in the long term use up more cpu time and battery life.
In light of that I'm going to stop using a task killer, because I've pretty much been using one from the start and I have pretty poor battery life. To the point even that I might look into getting another battery.