From your description seems more likely that you changed something in your system that is now greatly affecting performance, or some hardware issue, one possibility that comes to mind, is that you are running out of disk space.
As for the 'experimental' features in the release notes, I think you misread, these refer to supporting not yet released OSes (OSX Mountain Lion and Windows 8) and don't affect you if you aren't running any of these OSs as Guests or Mountain Lion as Host.
Last edited by a moderator: Apr 6, 2012