If nothing else, this will continue to be "interesting."
That's the spirit. Too many people are comfortable with what they already know and don't want to learn anything new (my wife is a very good example here).
while others here say it's faster
Slower and faster are relative terms. I've never used KDE and it may very well be much faster than Gnome 3, but it's definitely not as fast as xfce. In any case, most DE's, even the heavy duty ones, don't take up much cpu and even a bare basic dual core will not lag.
There seems to be a number of bugs with Mint 12 and this is probably another one of them. This is why I initially asked you to try one of the earlier versions. If you've already used ubuntu before I'd actually suggest you try LMDE. It's not as difficult as people let on, and there are almost no breakages. And if you change your sources.list to point to latest, you're almost completely safe here.
Edit: I just like to recommend LMDE that's all.