I'd forgotten that text doesn't show up with a link submission. Here's what I posted originally: Not new, obviously, but an interesting story for those of us who don't know it, and some generally applicable lessons. "In 2003 it looks like Plan 9 failed simply because it fell short of being a compelling enough improvement on Unix to displace its ancestor. Compared to Plan 9, Unix creaks and clanks and has obvious rust spots, but it gets the job done well enough to hold its position. There is a lesson here for ambitious system architects: the most dangerous enemy of a better solution is an existing codebase that is just good enough."