I've always looked at Scala as a great language to go to if you don't want to be on the .Net stack. But if you're happy with the .Net ecosystem, the combination of C# and F# are very tough to beat. The tooling is great, and the languages are really well thought out.

I don't really know what benefits there are to gain from using Scala on .Net other than the fact that it's cool that it could be done.