I've used it, and am still using it, to generate lots of value in a very large org. Having a language where I can bring Go, Node, etc developers over and get relatively better performance without having to teach OOP and all the implicit conventions that are on the C# side is a bit like a cheat code. With modern .NET, its better than Java perf, with better GC, and having the ability to code generic Python/JS looking code whilst still having type checking (HM inference). There are C# libraries we do use but with standard templates for those few with patterns to interface to mostly F# layers you can get very far in a style of code more fitting of a higher more dynamic language. Ease of use vs perf, its kind of in the middle - and it has also benefited from C# features (e.g. spans recently)

Its not one feature with F# IMO, its little things that add up which generally is the reason it is hard to convince someone to use it. To the point when the developers (under my directive) had to write two products in C# they argued with me to switch back.

I used it for many years but ended up switching to C#. The language needs better refactoring tools. And for that it needs something like Roslyn. The existing compiler library is too slow.