I have tried multiple Task Killers since moving over to the Android platform. Definitely, ATK is my favorite App for clearing system memory from unused/unclosed applications. Adding it as a widgit, and having the one touch kill function, once you have setup the app to only close the apps you want closed is a nice touch. The timed function however doesn't seem to always work, which would be the only downfall of the app. One thing I would like for the developers to add into the app is memory clean functionality, to help reclaim memory blocks that have zombied processes or are just idle.