
A lot of us kept thinking we needed a big ground breaking feature that would shake things up as much as Smart Bones. Personally I think there was more than one feature that really broke new ground. Of course I love bones... so any improvements to bones is good.
My favs:
The new bone constraints (Independent angle, bone squetch scaling, target bones)
Smooth bone joint (tricky to explain but easy to understand... awesome!)
Bone hiding!!!!! (finally! And point hiding too... but... I like bone hiding.

The SUPER FAST PREVIEW RENDERS!!!
That is going to save TONS OF TIME! Preview animation now renders as fast as playback in Anime Studio! Cool freaking beans!
Not only a help for super fast production previews and timing, it will help out those of use who need to demonstrate file rigging and construction curves because it can render the "interface" elements like bones and vectors directly to a movie file. And of course it's as fast to render as play back in Anime Studio.
And of course MULTIPLE OPEN DOCUMENTS!!!
Another "about time" feature. That one blew me away.

I am still trying to get use to this. You "forget" that opening a new file doesn't close the current file. If you don't pay attention you suddenly realize you have 10 documents open.