I have had the Mac OSX Lion theme theme installed for a month or two now, and am ready to either try a new theme, or go back to the default Unity theme.
How can I completely remove this theme?
From the link, I gather that you've installed the theme by adding the repository and installed it like any regular program from Software Center /
These commands should undo what installing the theme effectively did, (all the extra packages gotten for the theme should be removed). As for CompizConfig Settings Manager and Gnome Tweak Tool, they are handy even if you don't want the theme, so it's okay to have them on your system, just undo any changes that you might have done.
About resetting all themes and reverting back to the original, take a look at How to reset all themes?
This theme seems to have multiple components to it, but here are the basics:
First, go to System Settings>Appearance, and choose Ambiance as the theme (this will reset the theme).
Next for the Apple Logo (if you installed this) to return to the default logo, you need to reinstall Unity.
You can disable Cairo-Dock in your start up applications, or simply uninstall it if you choose.
Finally, you can remove the theme's files from