Well check it out, there are pros and cons when it comes to task killers. There has been a thread already discussing this topic. Pretty much what you are going to hear from most of the developers and all of the other people on this forum, as well as just about any other, task killers are "bad". The reason for this is because it ends these processes instantly and can mess things up. Sure it may save you some battery at first, but it also can cost you battery. What I have come to do is, I have a few apps on my phone that I use to monitor my systems resources. These apps use RAM, but not much so I value them greatly.
I personally used to use task killers when I noticed that my phone had very low RAM, or was noticably slow. so I would select some apps to kill off; which I deemed ok to kill. Problem solved for that moment I guess.
But now that I am a root user (You are going to hear a lot about being root on this site lol as well as all others. Its a way of life for most of us on here) I have found an app called 'Autokiller', and what this app does is, it modifies the phones normal way it deals with killing apps and ending processes, the safe way. So by using this app I can designate how much RAM I want it to try to manage and keep free. The safe way. Using task killers are pretty much like cutting a chickens head off, its just wrong and not done right.(best I could think of)
Well im sure I left something out somewhere, so I'm sure someone will jump in on this one and throw down some more info that I'm sure that I left out.
Hope this helped a bit