I have a big problem with Unity in terms of speed (I don't remember having this sort of problems with Gnome 2.x), my pc became slow when switching between the menus (in the same application).
Using the global menu or the normal menu for applications that haven't been ported yet. I have a Asus 1215N netbook.
I think the problem comes from the theme because this doesn't happens with Gnome3 Fallback or Gnome-Shell, but it happens with Unity-2D.
How can I solve this problem ?