This version includes mostly GUI changes and Mission Control add ons.
So what is new? The first thing i noticed is a redesigned login screen and a nice animation from login screen to the desktop.
The Mission Control (formerly Spaces) preferences got 2 additions and there is an Mission Control application now, so you can put it in your dock. (i think Mission Control was available as application since DP1 but now its inside the Applications folder instead Core Services)
You can add desktops now right from Mission Control by clicking "+" and close spaces as well.
The new scrollbars change color depending on the background so they are better visible on dark backgrounds.
The Dashboard got a new icon to switch to the next space.
New Desktop wallpapers.
That is all i see so far, but i guess there will be more new stuff i discover in the next days.
So stay tuned.
For more details check my other posts about Lion: