Ask HN: Has 9p (plan 9 protocol) ever been used seriously?

The question is pretty much exactly what it says on the tin. I've been teaching myself Limbo programming lately and studying the design of Inferno (including with the Plan 9 protocol which inspired many aspects of the OS) but I'm not really finding many applications that really use the 9P/Styx protocol on the internet. It seems like Plan9 never really took off, neither did Inferno.

If you know of any serious usage of the 9P protocol or have experience working on it, or any takes on it, it'd be very educational!