I use C11 atomics pretty regularly. While lock-free data structures are tough to get right, there are other uses of atomics that are easy. For example, portable lock-free multithreaded statistics counters.

Indeed, C11 and C18 don't bring a lot. I'm glad that they don't because backwards compatibility and roughly predictable development of the language is important to me.

I have been meaning to learn the Plan 9 dialect of C but haven't gotten around to it.