Actually, you don't really need to clean up after Linux, it deletes the temp files on shutdown. That command only cleans it up for your current session. If you were running a server, or some piece of critical hardware that does not shut down, then I would say it wouldn't hurt to clean it every now and then. Remember, this isn't Microsoft. :)
As for Ubuntu Tweak, I've never used it, although a quick search reveals that it is no longer being maintained. Personally, if a piece of software is no longer being updated and supported, I get rid of it.
Hope that helps!