Just to post a related experience, I'm using Ubuntu 12.04 (Compiz default) with the latest recommended graphics drivers for Nvidia. I wanted to play with the 3D Cube effect as well and used a good guide, so I installed CCSM (CompizConfig Settings Manager) and followed the instructions. Well, after I was done having my fun (and being a bit annoyed with the way the cube was functioning), I decided to go to Preferences and reset to defaults.
It crippled Unity; no dash, no menu bar. I couldn't even Ctrl + Alt + T to open a Terminal.
I would later come to find many people recommend against using CCSM at all; if you look, CCSM hasn't been updated since 2008 and Compiz has made some significant changes since then.
I attempted to recover the installation by going into recovery mode at the GRUB menu, but it still seems to behave weirdly.
The guy on this page with the highest rated answer sums this up pretty well (read the whole post):
Ask Ubuntu
I'm one who likes taking things apart, but it's rather difficult when you're trying to take something apart and you can't see what it is you're working with. If you're completely ignorant of how Linux works, install a distro, then try and figure it out, you won't be able. The average person isn't going to have a clue where to start. So you open a terminal, then what? You don't know the commands. Reading through the available help files still doesn't provide you with much of anything. From what I've gathered, the best way to go about learning Linux isn't to dive head first, but to read some books/articles/etc. It's an off-topic rant anyway.