I've been waiting for this one for what seems like forever. I really enjoyed working with Unity 3 while I was at SCAD, though I never had the opportunity to use it in any of my classes. We used UDK in my Animation for Games class with professor Cookson, and I often got into arguments with him about which engine was better suited to game design students. He (correctly) made the case that Unity required too much of an understanding of programming before you could get an animated character working, while in UDK, you only need the briefest introduction to Kismet before you get to work making a character controller and animtree.
It was about then that the first E3 trailers for Unity 4 and Mecanim started showing up and we got to see the new animation system planned for the next release of Unity... 6 months later, it's finally out! I downloaded Unity 4 last night and look forward to playing around with it today. The new animation system, Mecanim, looks like it will be a lot of fun to work with. http://unity3d.com/unity/mecanim/
You can try it out for free here: http://unity3d.com/
