I, too, can make a list of improvements that would boost sales, I would think.
One thing I find is a big boost that no one mentions is it's near flawless import of Photoshop brushes. I've only had to make a few tweaks to the many I've imported.
I'm also trying out ArtRage and Krita (I primarily use Photoshop) and I have spend hours in those pother apps to get my PS brushes to work, and haven't been able to.
One major thing I find odd about ASP is I can't easily use a reference image. You can't have documentys open side by side and you can't have a separate reference window you can color pick from.