i used 2004 for ages on snow leopard and it was fine. i now have 2011 and would say it crawls along in comparison. i have i nice up to date MBP and Office 2011 is the only application that really shows any lag. Microsoft's big claim for this release was how spritely it would be. Apart from the lag in daily use, 2011 also works fine. I did seriously consider going back to 2004.