There isn't really any case against F#, but you have to understand the context of the situation we, as developers, are in currently.
The multi-core architecture is still in it's infancy. The major driving force to change single-threaded apps over to a parrellel architecture is going to take time.
F# is very useful for a number of reasons, parrallelism being one of them, but not the only one. Functional programming is also extremely useful for scientific purposes. This will be huge in many sectors.
However, the way you're wording your question it sounds like you're stipulating that F# is already fighting a losing battle, which is definitely not the case. I've talked to many scientists to date that are using things such as MatLab and the like, and a lot of them are already aware of F#, and excited about it.
