5 different machines from an aging Powerbook G4 12" to a late 2007 Mac Pro, all ok and without issues. Main benefit we've seen is the wireless in the Macbook Pros and the addition of the gesture 'right click' on these same machines. Over the next few days I'm sure we'll bump against the other improvements. All machines were updated using the large Combo updater since we seem to get the fewest issues with this route.