Here are a few more suggestions (working on B_2 version, OSX):
* hierarchy view should retain expanded/collapsed state of its nodes when toggling show sprites on-off.
* There should be a way to expand the names of the objects(sprites/bones) in the timeline view. Currently they are limited to the width of the playback/pause/forward etc buttons ribbon.
* I think it would be useful to be able to add keyframes only of: Rotation, Position, Scale, or combination of the above. Maybe have 3 checkboxes?
* when you wish to scale only towards one side, you can press Alt while rescaling. If you press the alt key before click-dragging, it creates a bone, so the only way to lock rescaling towards one side, is to press the Alt key after you have already started rescaling the item (by dragging one of the scale-handles). But this retains any scaling you did before pressing the Alt. This makes it impossible to scale in one direction without loosing the original centering!
It's more meaningful if at the moment you press the alt key, the not-yet-committed rescaling gets reset (and not accumulated) and only the scaling towards the new direction is effected.
(Pardon me if I didn't make clear the problem/solution - I'm not a native speaker - but still I think it's a very important point to convey so please ask me and I'll prepare a video that demonstrates both behaviors)
* Would be useful to have a way to copy/paste between frames the hierarchy(parent) and Z-order of a sprite/bone, but not necessarily have it replicated to all frames in the animation