I upgraded to 201204 using mintupdate.
After getting past the usual issues with VirtualBox I was able to log in, but got no menus, just black bars top and bottom. On the right of the bottom black bar, I was able to switch windows, but apart from that I was only able to use the right click on the desktop menu. This was the same whether I selected GNOME, Classic or Cinnamon.
After a little puzzling, I checked my VirtualBox machine settings and found 3D acceleration was disabled. Stopping the LMDE guest, enabling 3D acceleration and restarting gave me a workable cinnamon desktop.
So far, it's almost as good as the old GNOME2 interface, but not quite. Next stop MATE?