I played with Xamarin Studio + F# + OS X about a year or two ago. Right away I noticed that F# is a second class citizen in Xamarin. Weird bugs, weird warnings, unfinished parts, hard to find help online and in IRC channel. And since it's a smaller language, there are 1/100th the number of tutorials/resources at much lower quality. Anyone who wanted to run my app on Linux or Mac had to deal with Mono 2 vs Mono 3. Despite spending a lot of time, I never figured out how to compile a windows binary on Mac or a Mac binary on Visual Studio (or how to have a project folder that works both in Xamarin and Visual studio without both git problems and linking problems). Starting a C# project is a pleasant experience, starting a F# required searching for add-ons and manual configuring (both in Xam and VS). I couldn't even run the iOS sample app without paying hundreds of dollars for the full version because the iOS libraries made the binary (of the one page sample app) to big for the trial version. Response in IRC was "yeah, we know. Oh well".

A real shame. I'd love to dedicate myself to an open source functional language with a GUI toolkit that runs all platforms, desktop and mobile.