I have used Clean Master in the past. It does a good job of cleaning junk and outdated files from your phone.
However, I usually install it, let it do its thing, and then uninstall it. The app has a nasty habit of bugging you with 3-4 notifications a day. "You can clean X amount of memory", which turns out to be pictures, videos, and other things that most people don't want to get rid of.
It will also monitor your memory usage and ask tell you that your memory (RAM) is nearly full. It wants to boost your RAM by closing programs that are running in the background. This is completely unnecessary for Android phones as using more RAM is a good thing. Killing them off actually eats your battery, as they will only restart themselves in a few minutes.
So, if you've got useless stuff gumming up your phone, use it then uninstall it. That's my two cents.
Posted via the Android Central App