I have used it in production at small companies (i.e. not Amazon, as some other commenters mention) for things that needed very high reliability. It helped us f

I have used it in production at small companies (i.e. not Amazon, as some other commenters mention) for things that needed very high reliability. It helped us find a few race conditions that took > 20 steps to reproduce, that I would probably never have found otherwise, and also helped us be very confident in our fixes. I strongly recommend it if you work in scenarios where race conditions can have very bad consequences. OTOH, I also had 2-3 failed efforts to learn the language and tooling before it really stuck, and I still mostly just use the pluscal syntax.