As someone who writes a fair bit of c# making switch and if's into expressions and adding Discriminated Unions (which they are actually working on) are my biggest "please give me this."
Plus side I dabble in f# which is so much more expressive.
Same for me in the Scala vs. Java world, it's hard once you get used to how awesome expressions over statements and algebraic data types/case enums/"discriminated unions" are. But I haven't done much C# (yet) myself, could you clarify for me: does C# have discriminated unions? I didn't think the language supported that (only F# has them)?
The c# team is working on a version of them they are calling Typed Unions, not guaranteed yet but there is an official proposal that I believe is 2 weeks old.