I'm curious if circuit breaking is better at the method level of the code ala Hystrix or at the network level. We need more in-the-wild experience reports I think...

The thing you can do at the code level is integrate it with your exceptions and protect against software integration bugs. Imagine that your RPC against a new version of a service fails because of bad data. With a library level circuit breaker, you can catch the failed exception and blacklist the new version of the service. With the network level, your resolution of failure detection is more limited.