First of all: the animation tools look promising. I'm really excited. But I'd like to see few features in it.

The animation timeline would benefit a LOT from the ability to shift frames via keyboard commands. I'll use Maya as an example: in Maya you can map shortcuts for add and remove in-between frames. What it means is, that for example I hit some key = frames after the frame I'm in, empty or not, move one frame to the right. I hit some other key, they move to the left. It's a small thing, but makes a world of difference when you're doing timing tweaks, as it is just so much faster to do this way, than dragging elements. As a professional animator, all I can say, that the thing that matters in the end of the day is a fluid workflow.

Also the timeline (and many other aspects of the GUI) is pretty much unusable with hi-resolution devices like Cintiq Companion 2 and Surface Pro 4. It is just so tiny when you go up from the 1080p resolution. Please make it so, that the users can scale the GUI elements, even if the implementation would be so, that it would have just readymade presets like 1x, 1.5x, 2x, and so on. At the moment it is really painful to try to animate, or even use Krita on those devices because of this thing.

Also the ability to colour code frames would be nice bonus feature, so the animators could easily see which frames are the true keyframes, which are the true in-betweens.

[bug]PS. also the CTRL-drag-copy, please fix it ASAP! [/bug]

Btw. the Onion skin in Krita is one of the best implementations I've seen. Very good job!