Not OP but I've used Crystal in production at 3 companies: Qualtrics, InVision, and my own side-company (~40 employees) which I briefly mention in this podcast[0] from a few months ago.
We do, but only for a few smaller services. It's great, but most of the things we do aren't CPU bound, so we use Ruby. Personally, it's become my default for side projects.
Very cool. Have you written anything about your experience with it in prod and on side projects? I'd be interested to learn more.