FWIW I just downloaded OnyX 2.8.1 for Mavericks from http://www.titanium.free.fr/downloadonyx.php. It was a drag and drop install (although there is an uninstaller in the menu), and as far as I can tell with cursory testing it works as advertised. (After convincing System Preferences > Security & Privacy to let it run that is.)
If we knew what it was we were doing, it wouldn't be called research, would it?
