I think the general idea is that if you make your yield points explicit, you see them yourself, and if you generally try for 100% unit test coverage, you end up nudging yourself towards fewer yield points, a simpler state machine, and better karma overall.

The complexity you see affects yourself more than the complexity you don't.

I rather agree.

FWIW my friend Abhijit Menon-Sen wrote a blog post on the matter last year, about some code with excellent test coverage and explicit yield points: http://toroid.org/callback-heaven