Having made the analogous switch from Java to Scala, I think it's the good devs that benefit the most. Functional languages give you more scope for factoring out commonality, avoiding repetition, reusing existing library functionality - exactly the things that make good devs better than bad devs.

I do, because many of our requirements are purely functional. E.g. Turn a bunch of database queries into a user-friendly report.

They're eager to use the latest enhancements to C# that come from the functional world (e.g. lambdas, await/async), but it's impossible to get them to give up their mutable variables and null pointers.