InfoCentral, there are no major changes in most parts of Blender. They give us more, not only different.

I don't know which parts actually make it to 2.5 in time, but animation changes are better editors (NLA I think, maybe other areas, also making as many things animatable as possible), so most of what we know is just more easily usable. I think that Jaguarandi branch of raytracing looks interesting as well as Freestyle (better toon renders for me, yay). Also there's something major coming in NURBS side.

(OK, maybe I read too much rumors...)

I think the much discussed new UI stuff may be minor stuff once you get used to it -- maybe we get all Chrismas presents this year, no matter what is our favorite area...