This seems like the place to report bugs, from what I can tell? If not, I'm not sure where, but I'm happy to post elsewhere.
My Nvidia GeForce GT 420M seems to have a hard time with extra tails on the paintbrush, eraser, clone stamp and recolor tools. As far as I can tell, no others are effected. Additionally, this problem does not arise on the integrated graphics. The first screenshot (mostly black) is when the program is first opened, the second is after a different program has been switched the foreground and back to PDN, which makes all of the darkness go away.
Screenshot 1
Screenshot 2
(linked as they were slightly too big to attach)
Loving it so far, but I just found the 4.0 alpha today.
