I'm always surprised that F# didn't take off. It's a great language and in addition to the strenghts of ML you have the .net ecosystem and Microsoft behind it.
It took awhile before it seemed that Microsoft was truly behind it. I tried looking into it when version 2.0 was released and it was a pain in the ass trying to get it to work with Visual Studio 2010 Express. I was not a professional programmer at that time so I didn't have access to Visual Studio Pro. That experience turned me off to the language and I never really went back to look at it.
There’s some hedge funds using F#. C# has historically been popular in certain parts of finance any many of those shops are now exclusively using F# for new code.
Personally, F# is nice and all, but the lack of higher kinded types rubs me the wrong way.
