Yes, some people use F#
I saw a presentation not long ago from a CIO in a large insurance firm; they'd recently migrated some core apps to F#. Got a huge performance boost too. (For the usual reason: some abstractions are more convenient to implement in a dynamic, functional language, so certain classes of problems can be easily addressed with more efficient algorithms.)
ML variants (F#, OCaml, etc) have been around a long time, and they have a market. Mostly it's in scientific and numerical applications, research, etc, but they're well-suited to some business apps.