Coroutines (for I/O) - why better than callbacks? (Score 1)

RE you talk on proposed standard async IO and tulip. I still don't understand why callbacks are bad, and how coroutines are better? They seem quite obscure to me (although I have to admit I have very modest experience with Python), and difficult to reason about. More specific example: my current project is I/O heavy, I use a dedicated IO thread with libcurl/pycurl multi interface, simple event loop & timers - i.e., pretty much all logic is event-driven / implemented in callbacks. Why would I want to use tulip (or anything coroutine-based) instead?