Hi i love paint.net and find it essential to the work i do.
I only have two problems with the new version, when i am using hardware acceleration the screen flashes black and white and the mouse cursor leaves weird trails all over the screen turning off hardware acceleration fixes the problem so its not a big deal and its probably due to my laptop having two GPUs and using Nvidia optimus to switch between them.
my big problem though is the eraser tool, i do a lot of pixel artwork zoomed in very close with a size 1 eraser and the centering for the tool seems to be off slightly like i will have the circle almost completely over the pixel i want to erase but the pixel above or to the right will disappear instead.