I only skimmed the article, but is the argument basically that fibers suck because library/DLL authors suck and use TLS instead of passing around an explicitly caller-initialized context pointer? So you can't freely use DLLs from your fibers because they might rely on TLS that isn't fibers-aware?

If so, that's a pretty weak argument. I use coroutines/fibers quite a bit in personal projects, but learned long ago for a variety of reasons to avoid depending on third party libraries I didn't have source for - especially ones that try to do too much magic like TLS behind the scenes just to save me the trouble of supplying an instance/context pointer to every call.

Usually when I'm using fibers it's so I can have many of them, which means I'm using tiny stack sizes, which means I'm not casually calling into third party libraries I can't easily audit and control anyways. If I weren't making many, I'd just use full-blown threads.