I'm an F# developer, but still decided to not use F# to build an android app. Dealing with the UI libraries like support.v4 was just too painful from a functional perspective. If you don't need any object oriented dependencies, then it's smooth sailing.
I've only heard that in context of A: missing tooling, B: Microsoft, in their quest to make customers feel C# is still the real language and F#'s just some science toy. I've used F# for a Web UI via WebSharper and it was lovely. It's just a poor reflection on the state of UI kits if they don't work with F#.
