Hi! Im running the beta on a Mid 2011 iMac (2.7Ghz i5 / 16GB RAM - AMD Radeon JD 6770M) - everything is slooow and dragging things around is jerky, i can see the window refresh swoop down (like what used to happen when kernel panics kick in). There's no transparency, and windows flicker like crazy.. Is this a known driver issue with the 6770M? Does anyone have a fix? I made a time machine backup, so I can just revert back, but it'd be nicer to fix it if possible, especially as its running so well for some people.