Lets not get too hasty. Task killers can be handy when used properly. You should use a good one like SystemPanel.
http://androidforums.com/android-ap...task-killer-people-who-hate-task-killers.html It shows you exactly what your apps are doing in terms of cpu utilization, radio activity, etc. This gives you the tools you need to identify apps that have decided to smoke crack, gone whack on you, and of course stop them. This is nearly always what happens when you suddenly have a change in battery usage for the worse. Killing tasks willy nilly is a crutch but doesnt fix the problem.
The second thing a task killer can do is give you an easy way to stop apps that use a lot of battery and need to run in the background. Take trapster. It uses a lot of battery because it pulls down a lot of data and works with maps both of which stay lit up. This isnt a fault, it needs to do this to work. To stop it you need to switch to it and drill a menu. Or hit one button and kill all with a task killer which is faster and more convenient. The key here is you should exclude all apps which you use frequently from being killed. This way you are working with the memory management scheme instead of against it. What ends up happening is most of your tasks are not killed and will continue to be managed by android. Those that do get killed will probably not be needed anyways because you use them infrequently. Processes have many levels of activity, here is a cut and paste.....
An activity has essentially three states:
It is active or running when it is in the foreground of the screen (at the top of the activity stack for the current task). This is the activity that is the focus for the user's actions.
It is paused if it has lost focus but is still visible to the user. That is, another activity lies on top of it and that activity either is transparent or doesn't cover the full screen, so some of the paused activity can show through. A paused activity is completely alive (it maintains all state and member information and remains attached to the window manager), but can be killed by the system in extreme low memory situations.
It is stopped if it is completely obscured by another activity. It still retains all state and member information. However, it is no longer visible to the user so its window is hidden and it will often be killed by the system when memory is needed elsewhere..... End cut and paste.
The last thing memory management does is kill apps that it assumes are no longer needed after a time, the concept being that the task has probably been abandoned and it will instead cache new data in expectation of coming events.
So, I guess to sum it up task killers should be looked at as tools to deal with specific problems and they should be set up and used in a way that works with memory management and not against it.