I'd say, from the perspective of newbie to smartphones, treos, palms, wm..I can't give an authoritative review of the differences and improvements...it seemed more responsive and there were no delays when I make any selections, which I'd noticed with the original 5.0. There are some minor things that are kind of cool, like an actual mute button on the screen during a call. Initially it looks the same though appearancewise. Still finding out things as I go. Here's something I found that might be more helpful. An actual comparison of the versions.
http://www.microsoft.com/windowsmobi...n-compare.mspx