Someone pointed me at Greenlets the other day, and I'm really quite excited about them. This fully addresses the Limitations of Coroutines via Enhanced Generators I spoke of earlier. I see that "some very smart people" have gone down the path of tying it together with kqueue and select.poll along with an IO-based scheduler.
Greenlets look polished enough, but I sure wish the other stuff was polished and documented so that I could use it in production. The pragmatist in me (which doesn't come out very often) is still insisting that Twisted is still the safer route in the near term even if it is more irritating to code because of its asynchronous nature.