Edit: just before somebody starts whining about it, I ain't got no problems with NET on its own, but the barrier to proficiency in it from a functional universe is needlessly high, and if F# had a stronger core it would be something non NET programmers could pick up along the way rather than continuously bash their heads into while doing rather menial work.

I don't want to sound whiny either but it's such a punch in the gut when someone sees me struggling with basic FP stuff in F#, just because I guess I'm so proud of what I've learned about FP in other languages.

There's also some stuff that F# is missing, but it hasn't screwed me yet because I still haven't figured out enough about all the NET classes.