Gotta say the new UI (well, what you can see anyway =P ) looks slick, and way more user friendly.
I've given the Lite version a go and I have some thoughts/suggestions.
One feature that this tool will need is onion skinning. Especially if you want it to be competitive when compared to other software.
After trying it out, the way the program currently handles Z ordering is clunky. In fact, if you do not check the pdf's or the shortcuts option in help, you will likely not even know it's there. I'd suggest adding a tree view of the Z order, and buttons in the ui for moving the selected item(s) one step back/forward, and for moving to the back/front completely.
I can't comment on action points/collision rectangles since they're not available in the Lite version. Though those (especially collision rectangles) are the features that I'm really interested in.
Hope you can make this product the best it can be.
Edit: Motion tweeing is probably good to add as an option too.