I'm CTO of a software firm with a large existing codebase (all C#) and a sizable engineering team. I can see how certain parts of the code would be far easier to write in F#, resulting in faster development time, fewer bugs, easier parallel implementations, etc., basically overall productivity gains for my team. However, I can also see several productivity pitfalls of introducing F#, namely:
1) Everyone has to learn F#, and it's not as trivial as switching from, say, Java to C#. Team members that have not learned F# will be unable to work on F# parts of the codebase.
2) The pool of hireable F# programmers, as of now (Dec 2010) is non-existent. Search various software engineer resume databases for "F#", way less than 1% of resumes contain the keyword.
3) Community support as of now (Dec 2010) is less available. You can google almost any problem in C# and find someone that has already dealt with it, not so with F#. Third party tool support (NUnit, Resharper etc) is also sketchy.
I realize that this is a bit Catch-22, i.e. if people like me don't use F# then the community and tools will never materialize, etc. But, I've got a company to run, and I can be cutting edge but not bleeding edge.
Any other pitfalls I'm not considering? Or anyone care to rebut the pitfalls I've mentioned? I think this is an important discussion and would love to hear your counter-arguments in this public forum that may do a lot to increase F# adoption by industry.