This strucks me as great news as in the past I used FUSE2 and when I moved to AS3 I found myself looking for a similar alternative but not really finding one as good or widely accepted as FUSE2.
The I came across Tweener, and that's what i currently use to power all my projects, it's simple, lightweight and most important easy to use.

Normally this would be the end of the story for me, but somehow Tweener is lacking some funcionalities that would like so i moved to Boostworthy's engine and again I found myself lacking some of the things i had in Tweener. So I kept searching and found Go, that altough it's not an Engine per se allows me to have all the functionality I want by extending it.

Also i found a great tool to ease my decision, and yours, Moses's TweenBencher. It's a great tool to test out all the different Tweener and see their advantages and disavantages. Be sure to check it out.

But most importantly I came across Moses's proposal to Adobe for a Core Animation Library and after reading it I must say that I agree with it to it's full extent. So be sure to check it out, and to make your voice heard if you agree, or not, with it.