Interesting - we run a pretty large entirely eventlet-based system, so I'm excited to try this out on that. That said, our threads often number in the thousands, so I'm unsure how this would cope with that.
I've had it running for about five hundred concurrent. I purposefully made it something you have to checkout yourself so that it's trivial to add filters in if you want to limit what you're seeing.
We use eventlet heavily and this is great. I have always wanted something like this.