I'm on the data team at Librato, happy to answer any questions. Some of the Librato team will also be at ReInvent next week, can discuss more in person for others attending.
Rather than build your own, did you consider moving to another distributed stream processing platform such as Spark Streaming or Flink? If so, curious to know what disqualified them.
So this is definitely not a dig at any framework. If we were starting to build stream processing into our infrastructure today we would most likely start on an existing framework. Also, I imagine as our needs grow we will leverage these frameworks in future proof-of-concept streaming projects that may or may not make sense to move to Superchief.