I would like to use F# but don't because of .NET. I've been impressed with Caml (but not the "O") since I discovered it years ago and was interested in F# as soon as I heard of it. The problem was that I had no interest in developing on Windows, and Mono didn't look appealing either. With the advent of .NET Core, it looked like F# was finally going to be convenient for cross-platform development. I spent a few days downloading various releases and trying to get them working on a few different Windows machines before giving up. I'm not a professional programmer but write code for research. I decided that if I was having that much trouble setting up a working environment before even starting on the substantial effort required to understand the ecosystem, it was unsuitable for sharing work with colleagues or introducing to students. My story may seem irrelevant, since discussion of F# seems to always assume that you are already a .NET developer, but just remember that .NET itself is a major hurdle.
.NET is a big advantage of F#. Like with Scala and JVM, it gives you access to a mainstream ecosystem of libraries. A lack of libraries is usually what makes niche languages unsuitable for production, but F# handily side-steps this. Arguably, F# has a larger ecosystem than C#, since it can also consume JS libraries using Fable!
Mono is no longer required to get started with F#. All you need now is .NET Core.
