Oh, nice. iirc, I tried it when online editing first appeared on Github, and it was a bit finicky about rebuilding the page afterwards. Good to hear it works now.

I used prose.io for a while, but ran into a few cases where the preview didn't match what Github generated. It looks like there's a whole new interface since the last time I used Prose, so perhaps that's not an issue anymore. It supports image uploads now, too.