Some time ago, I discovered Krita, from David Revoy's blog posts, and I was following it's development. Lately, I tried it on Windows, but I found it to be very unstable, so I decided to give it a try along with Ubuntu (which I used quite a bit on my personal laptop... but only for documents stuff, internet and email... for painting, 3D and work, I usually run on Windows). Read more to watch a timelapse :D
