I didn't have any problems with doing a fresh install of Quantal. I used 12.04 and with the updates lots of Unity bugs were fixed. Now, with 12.10, I can say that the 90% of those bugs are fixed, and Unity is very smooth for my laptopt -I can run windows effects now! The only con I see is that if I install a restricted driver it's not smooth and it's slow (and only the NVIDIA experimental driver worked), so I'm happy using Nouveau -the same happened to me with GNOME Shell and KDE.
Great work, I used to use Mint because of Unity but for each update and bug fix I love more Ubuntu and Unity!
BTW, greetings to all, I'm new here -don't eat me