Yeah, something like a coroutine would be a fine place to use them. And I'm happy when languages do support CPS, even if I don't often use it.

Breaks in loops seem fine to me, because I'm comfortable with the whole thing being syntactic sugar for gotos. (Of course, parallelized foreach loops and such can reasonably have a very different basis, but there are still plenty of times a plain sequential loop is the most useful thing.) If one conceptualized all of one's looping through tail recursion, breaking would be the same problem as mid-function return, of course...