It's a massive win, and I would question the credibility of any systems programmer that doesn't recognize that as soon as they understand the wrapper arrangement. I would have to assume that such people are going around making egregious errors in how they're using mutexes in their C-like code, and are the reason Rust is such an important language to roll out everywhere.

The only time I've ever needed a Mutex<()> so far with Rust is when I had to interop with a C library which itself was not thread safe (unprotected use of global variables), so I needed to lock the placeholder mutex each time I called one of the C functions.