Git itself is a distributed VCS, so the GitHub downtime shouldn't have been too devestating to most people. However, speaking as somebody who uses GitHub Pages a lot and had it go down at one of the worst possible times for me, I can say that this postmortem definitely quenched any possibility of me considering moving somewhere else, since I am confident my data/uptime is as safe with them as it could be with anybody.

Everybody suffers from downtime. It's how you handle it that matters.