What a mistake it was to upgrade to Mountain Lion.
So many little irritations that I will not go into them all. I sure wasn't aware that I would loose all of my mailboxes. I used them to store emails related to a given subject that I wanted to keep. I suppose I was naieve to think they were safe there. Can't retrieve anything because- again I was unaware that Time Machine would be erased and start new from the moment of installing Mountain Lion.
A couple of little irritations. 1. Can't get the mouse to work right. Really tough to highlite and almost impossible to grab and move a window without it immediately dissappearing into the dock - usually takes several tries just to grab and move a window. I have made many changes to the mouse in Preferences with only slight improvement. Other things seem like ML goes backwards. For example with SL the contents of a folder could be resized by a simple slider at the bottome of the window. Now I have to go to preferences and resize if I want to enlarge or shrink. What a genious move that was. Also the same folder in SL would show you how many items were in the folder. ML gives no info. There is more but suffice it to say IMO it is a lousy upgrade.
iMac (24-inch Early 2009), OS X Mountain Lion (10.8.3)