A couple things that would be great in this already awesome application.
Toggle play all keyframes - as of now whenever I create new keyframes for animation I have to press play for every new animated layer even whilst the others are playing, there should be an option to play all automatically.
Wider view of keyframes - the left to right slider for keyframes is limiting for those who want to do longer animations as you can only see a certain amount of frames.
Move keyframes - Being able to move keyframes around would be great, I don't currently see an option for this. Please correct me if I am mistaken.
Scrub through timeline - a smoother version of what we have now, still a bit tricky to animate with only being able to flip through each frame individually.