Upgraded from Snow Leopard to Mountain Lion yesterday. Big improvement! The only thing so far that does not seem to be working is activating the Tab View in Safari using my Magic Mouse. When I pinch, nothing happens. I looked at the settings for my mouse in System Preferences, but pinching is not listed as an option at all. Can you only activate Tab View with a trackpad and not with a MM? Or is something wrong? Thanks for your reply!