Right, the hung nodes issue is probably least related to kops (though it'd be great if in the future, kops could leverage something like node-problem-detector to mitigate similar issues). Of the other issues, the incorrectly applied cluster config (kops decided to update certs for all nodes and messed them up in the process, then proceeded to mess up the Route53 records for the cluster) is the most serious one, and also not likely easy to reproduce. Apart from that, kops has been an excellent tool and we've been very pleased with it.