It was quite some time I used ASP, but decided to get the new beta to try: I really like what you have done to the app! I like the fact that I can have multiple panels open (layers, colors) but I must say I would like them to be a bit more compact, especially the color editor. They are a bit too clunky now for my taste. Also I would like to be able to dock them in some way, and be able to open/close the whole sidebar at once... Having read your previous comments its not what you want to do with ASP, but it make my workflow more efficient.
I also like the fact that any action can be added to the top bar. I have set deselect, clear and erase blending mode in it, and this is very helpful for me. One little thing I would like to see is a kind of visual indicator when using the erase blend mode. Right now I can not see which mode is selected, and this might lead me to believe the brush or the program is not working properly, as it does not make marks. It would be solved if the button at the top bar showed some visual change when selected. It only has to be subtle, but it would help.