Well, Snow Leopard really wasn't a true refresh. It was more like a "service pack" type of update, so OSX really is overdue for a full update.
I hope that they finally add TRIM support for SSDs in the next update, as they are common place now and provide the most noticeable performance upgrade for your average user.
The other thing they really need to play catchup on are multi-touch and HTPC functionality (the lack of tablet computer optimizations and a native media center don't make sense for 2011). They have to compete w/ the Windows 8 release, and its set to run not just on Intel Cores, Atoms, and AMD chips as at present, but cell processors as well to make it on ultra-light tablets and the like:
http://www.youtube.com/watch?v=p92Qf...layer_embedded