Just upgraded to Mountain Lion. The first time I did, I had to go back to Lion because I was having so many problems with my BT keyboard and Magic Trackpad. They would disconnect and connect and become jittery and unresponsive randomly. I figured the problem would be fixed with 10.8.1 or certainly 10.8.2, but apparently not. I'm still having all the same problems with my MacBook Pro and bluetooth devices. I haven't had much success troubleshooting the problem, but I have noticed that the Apple Bluetooth Keyboard doesn't show up in the Keyboard preferences pane. It says "No Keyboard Found", which is strange, since 1) that's what I'm using to type this message, and 2) It does show up in the bluetooth menu in the menu bar. I wonder if this has something to do with it. I tried turning BT off and on again, and disconnecting and connecting the keyboard and trackpad. Sometimes that helps for a little while. But inevitably the problem returns. Anyone else having these issues and have you found a fix?