I've just tried the demo, and I have three words : "Oh My God". There are a million tiny tweaks, and all the ones I've found so far are lovely. The interface is better, the renderer is much faster, all the new stuff is integrated and easy to find. I haven't had time to really give the big new features a proper roadtest, but I've already decided to buy. Not sure how much it'll cost to upgrade from 5, but I'd actually pay full retail all over again for this if I had to. I was really happy with 5, but this is just so much better.