I decided to take a punt on this in view of today's 50% off Promo. Purchase, download, unzipping all went smoothly. When I tried to install, I got the alert saying it couldn't be installed as it was from an unidentified developer — my preferences are set to only install from identified developers. I found this bizarre, since the app is available on the Mac App Store.
I will change my preferences temporarily, but I find it frustrating.
Having installed it, although it is fairly straightforward even for someone who is not very experienced in graphic design, I found:
1. that it periodically becomes rather unresponsive to clicks — MacBook Air, using trackpad, not mouse;
2. when I saved my file, the Save dialog — in column view — did not respond properly to selection on the left panel … I clicked on Documents, but rather than showing the documents folder directly, it still showed home-folder/Documents/Other folders …, making navigation more difficult
3. having saved my xxx.capp, the app was still marking the drawing as "dirty", with the black spot on the red traffic light, and when closing asked me if I wanted to save the file which I had already saved.
I think I will soon manage to tame it, but there seems to be a fair amount of development still necessary.