Yeah I wouldn't spend time on F# on non-Windows until the community builds up more. So you probably want to try either OCaml or, if you're up for a bigger challenge, Haskell.
How are the Mac and Linux Mono versions? Are they production ready? It's not really about the "bigger challenge", but being able to ship code that solves real problems for clients.
This is actually my impression, that Mono isn't at the same level of performance than the windows counter-part. I guess we can expect with .Net Core to see improvements. But will the Mono runtime ever be as good as the CLR ? The CLR isn't open sourced. The whole open-sourcing happening in the .Net world is quite interesting, but It is also confusing the hell out of me.
