There is a very good reason not to run task killers. It kills off tasks that think they should still be running. In the long run, it ends up using more phone resource than if you just let them finish their job and shut down gracefully.
There is a lot of confusion about how the Android OS works. Tasks do not use resources unless they are active. This is a lot like the GPS task. It doesn't use any resource at all unless prompted by another task. But it you kill it off, it will have to restart from the beginning, using a lot more of the phone resource than if it had just been left alone.
Android can support hundreds of running tasks that use no resources at all. Killing off these tasks makes them rerun stuff that they would never haved needed to do if they had just been left alone.
I never run a taks killer myself and have zero problems with battery life or phone performance.