I recently installed Ubuntu 12.10 on a laptop and I noticed that they had removed the Unity 2D option. I previously used this option because the desktop would load much faster and the system was more responsive with it. Apparently Ubuntu is nearly unusable on this laptop with the default version of Unity.
So without the 2D version, I went looking for a quick fix to the slowness. It turns out that the GNOME desktop is still available in the repos, under the package name
So a quick
sudo apt-get install gnome-session-fallback, then a logout and selection of the gnome desktop had me back and working with a responsive system again.
This is a little disappointing since the laptop I am using isn't that antiquated, with its Intel Core 2 Duo CPU P8600 @ 2.40GHz and 4 GB of RAM. If Canonical wants their OS to run on everything from your smartphone to supercomputers, they need to step up their game and remember the little guy.