I think you confused "good job of Managing apps on its own" with what ATK does. ATK will kill the app only to have it start right back up to finish the sync it was trying to accomplish, this starts a kill, start up cycle. Kills your battery quickly. Android will allow apps to start and finish sync cycles. Also they do not run in the back ground, they will stay in your memory but will fall out when that memory is needed.
Good read. Task Killer -- Do I need one?
You guys got somethin' to say to me? Why don't you say it in the microphone. I got a backup mike right here. Check one two, testing, testing. Yup, they both workin' and guess what? They don't like no feedback, what's up?