I have -- we used Twisted (about 10k lines of code). Then switched to eventlet -- and the code reduced to about 5 or 6K. There were some issues with monkey-patching, but tests showed them, and we fixed them.
As someone mentioned, if they instead standardized on greenlet then monkeypatching talk wouldn't make sense.
Do you think this would be relevant if greenlets were adopted as a part of Python?