Magnificent. Sadly, it doesn't complement Tilesetter as much as I thought. Using Aseprite or Paint.net, you can simply copy the selection and paste it straight into Tilesetter without having to save the drawn sprite tile. Just select the drawn pixel art, CTRL-C (copy), go to Tilesetter, and CTRL-V (paste). Rinse/Repeat
But it's definitely a very good software for making pixel art. I also really like the built-in capabilities for animation. Although I really hope to see other more common features gets added, like: CTRL-A (Fill selection) and some more.
Still, since this is open source, I would highly recommend it!