IMO smooth operation is pretty hard to come by if you have a lot of apps jamming memory. Also, ATK and other apps such as this, really mess up your system. They did mine. I used to use them but had to uninstall because they destabilized smooth operation.
IMO, again, the only way to get truth lubricated-greased operation with many apps, such as I have (135 added apps, 247 total) is to root and use
AutoKiller Memory Optimizer - Android app on AppBrain It is not a task killer, but it sets parameters for smooth operation. Again, it's a root app. It's fantastic and I've never had a problem with operation since using it. Never.
Good luck!
Steven