When we added the equivalent to Rust, it was a bit controversial. But the idea of "an optional type is a list with zero or one items in it" is much more normal in functional places, and so a lot of people like it quite a bit too.
The fun thing is that the original design (N3527 over a decade ago) for std::optional specifically says it's not the container with exactly zero or one items, whereas I believe Rust's Option never made this claim and so recognising this isn't a U-turn.
