I'm going to keep this short because, well...it's 4am. I just beat the Diablo 3 Beta with the Wizard class. My overall impression: this is a HUGE improvement over Diablo 2.
The Good
Pretty much everything except what I talk about below. Navigation/movement is pretty much the same as Diablo 2. I did notice that there wasn't a good way to walk around with the map displayed, which is something I will miss, but it doesn't kill the game or anything. The effects for abilities were really solid, and the physics are amazing.