F# is the bomb. Once in a while I even consider running ASP on mono so I can use F#, then I realize I'd need a windows box with Visual Studio and decide against it.
That maybe a while ago, like when Ubuntu was 9.0 and you had to compile from source code in order to get sgen? Things are much better now. Since early this year, I've been running a web service written in C# serving one of my iOS apps. That piece of service has been running happily in a tiny VPS for half a year now. Installation of the Mono runtime was an easy apt-get.
Mono is completely installed by default on older versions of Ubuntu (8-11). The runtime with some development tools is installed in 12 and 13. You can get it on any version since 8 with apt-get.
Don Syme has added some interesting features to F# like type providers, so I think it is OK to say that F# has transcended its OCaml roots to become an interesting language in its own right.
Not to mention the approach to OOP is rather different in F#. It's syntactically and culturally different. Most OCaml programmers I know avoid OOP for the most part, whereas it's embraced to some extent in F#. Seems like a sort of "functional first, but feel free to use objects as you see fit" philosophy in F# versus a "functional always, objects are a failed experiment" philosophy in OCaml.
I don't mean to imply any judgment here, I'm just noting another difference between F# and OCaml.