Good question. You might want to mirror this question over on Deep-Six to get EAST's input.
I can tell you that I'm holding off on the upgrade (Got a free one for my laptop, and another for the desktop through a promotion) due to the persisting reports of "bugginess". I think I'll probably hold off until a service pack comes out. There's no dire need for me to upgrade at this time.
I guess it's a whole other ball of wax when you are buying a new machine, though.