I'm slowly making progress on ZenPaint, a simple animation tool for kids. I started writing it using PyGame, but hit the wall in terms of display, having to redefine my own widgets, etc. So I've taken a couple of step back and now I'm working on it using PyObjC. I keep waffling back and forth on whether to use Interface Builder or not. I don't find Interface Builder very intuitive at all, but maybe I need to buckle down and get good at it. Knowing about nibtool helps–at least I can do text diffs and simple renames from the command-line.
One thing I would like to point out, the Apple NSDocument FAQ is one of the best bits of documentation I've ever seen out of Apple. So I'm mentally translating it into Python and trying to apply it to ZenPaint. As soon as I can load and save files reliably I'll post the program and code up here for comments.