A couple minor interface changes - nothing major at all. Bones are a little different to handle but perform better now. Hair is a new interface and also has shader controls specifically for styling. Obviously, the claim-to-fame is the handling of Poser/DAZ content directly from within Carrara so no program hopping is required. If you do much with Poser, than C6 really is a must. Lot's of little speed improvements and cool stuff like the ocean primitive, faster blurry reflections, absorbtion. Personally, I'd have gotten it just for the Hair module alone since you can do so much more than just hair with it. The hair shader controls create very realistic anisotriopic hightlights. (you know, the way hair has highlights in bands) It's pretty sweet. I know for a fact that the programmers are aggressively fixing post release bugs so the next maintainence release ought to make this pretty solid.