I don't know, I'm not finding it hard to evaluate that at all.
I've had bad enough experiences with gevent in the (now fairly distant) past, and that's a well-established project, just a subtle one with a large blast radius. This has all of those problems, plus is _much_ larger and I don't think can possibly have been tested as widely as I would want. I get maybe there's a lot of test code, but I think this kind of thing you only really know when the rubber meets the road.