I find it relatively simple. Much simpler than C++ (obviously). For someone who can write C++ and has some experience wth OCaml/Haskell/F#, it's not a hard language.
Complex is the wrong word. Baffling is a better word. Or counterintuitive, or cumbersome. If “easy enough for someone with experience in C++, OCaml, Haskell, and F#” were the same thing as “not hard” then I don’t think this debate would come up so frequently.
I mean, you can't expect to learn a new language in a few days, it'll always take a bit of work. My feeling is that people complaining of the language being hard aren't putting the effort.
My experience is that Rust is a relatively small language which doesn't introduce a lot of new concepts. The syntax is quite intuitive, and the compiler super helpful. The borrower checker was the only new thing for me. I'm not an expert at all, but my experience is that after spending 2 weeks full-time reading books and experimenting, I was able to work professionally with the language without feeling too much friction.
On the other hand, after spending much more time on C++, I don't feel really comfortable with the language.