Another quick thought. Again, this program is already polished and excellent--I think "export" should be as simple as hitting ctrl/command-C with something selected and then pasting into a text file. This would be for quick little drawings without breaking flow in another file. Right now it seems like you have to export, choose a file name and location, open the new file, etc., etc.

And another quick thought. I haven't looked closely at your save format, but it'd be great if one could also have periodic autosave to *.txt or even autosave after every change. Layers, etc., would be lost, but I'd feel safer than leaving data in your "proprietary" format (which actually might be quite accessible) if I investigated it.