I have a late 2009 21.5 iMac 3.06 with 4GB RAM. After upgrading to ML, I have seen a nice improvement in the overall speed of my machine. That said, do you think I stand to gain any more speed by upgrading the RAM? I have 4 total slots and only 2 are in use (2x2GB). Is it worth spending the $50 and filling the two empty slots with 2x4GB for a total of 12GB RAM. Will I even notice a difference browsing Safari, using iTunes and iPhoto (the biggest pig)? Thanks all in advance!