This is my experience as well, although I can't speak for F#. Functional programming languages work, until you hit a performance wall and need to dig a bit lowe

This is my experience as well, although I can't speak for F#. Functional programming languages work, until you hit a performance wall and need to dig a bit lower in the stack. It is when things get ugly that they start to look like fancy calculators. Besides ATS (which is not very practical), only Common Lisp seems to accommodate to that (and maybe just because Lisp is old and had to deal with performance issues for decades), but it still lacks a state of the art GC.