Nota issues here. Things running pretty smoothly as usual, and super excited about the FCPX update. Man, no slowdowns what so ever for me... super smooth and super quick. (2010 iMac i3 4gb ram). But before yesterdays fcpx update, i'd get the beachball every now and again for 5-10 sec. So for me, all good. Sorry to hear some are having issues... that's never fun