I've had production daemons running for a few years on Mono. (SQL stuff, RabbitMQ)

In general, Mono (with or without F#) just works. I do all the development on Windows and VS, and then copy the binaries over to deploy. Downside is that stack traces don't read the pdbs so I don't get line number information.

F# Interactive has had some readline and other weird errors on Mono/Linux.