Holy crap. I don't think any other Jepsen post has ended with a simple "Recommendations: Use Zookeeper." I kind of miss the little ASCII dude flipping the table over in rage, but ZK must be doing something right. An interesting architecture suggestion: Zookeeper (which is CP) pointing at an AP data store. Writes won't always be available, but you have in a sense isolated that write unavailability, which could be an advantage.
Related: Datomic can be configured to use both Zookeeper and Riak, and the implementation is really clever: immutable data in Riak and strongly-consistent "pointers" in Zookeeper.