I'll have to add a shameless plug to the visual HTML5 editor in the browser that I've built. Also created with GWT, and using GreenSock JS for animations.
tweenui is very slick, I was playing with it some time ago, very well done! I like how you did ad campaigns, variations that kind of stuff. we don't have it at the moment, but do have much more advanced drawing/animation.
Available at http://tweenui.com/animator/
What do you think? How does it stack up?