I can't speak for anything other than the out-of-box-experience (OOBE)... but if it's any indication of what I can expect over the next week, this is one impressive build. Vector glass is a term I've heard used to describe this build. I'm not sure if something has changed, but icons looks very sharp regardless of how small/large they are scaled. Flip3D even seems to run more smoothly.
On the flip side, Windows Mail still doesn't support MSN/Hotmail like its cousin Windows Live Mail Desktop (sad, just sad)... and my Treo 700w is stuck with very limited connectivity (i.e. no ActiveSync functionality). So, by no means is this thing ready for release... but it's getting a lot better. I'd call this Beta 3 if it were up to me. :)
Check out my first batch of screen shots here:
http://windowsconnected.com/photos/vista/category1054.aspx
Note: I'm running a clean install of Vista RC1 on a Compaq/HP nc8000 laptop w/ 2GB RAM and a fairly weak 64MB ATI video card. Heck, even my USB drive was enabled for ReadyBoost - which is new to this build. Enjoy!