My late 2008 Aluminum 2GHz MB runs admirably even with 10.8. You just have to ensure plenty of RAM and HDD space are available so virtual memory isn't throwing a wrench into the speed. I don't see why you would want 10.7 over 10.6 though. I think I upgraded to 10.7 in the past but nothing big. I think I'm stuck in a 10.6 mindset.