On Cassandra, some CQL collection operations behaved well (adding elements to a set). Everything else Kyle tested there was demonstrated to lose data.
Kafka lost data all over the place under Jepson; though Kyle offered great respect to the team and expects them to deliver optionally configured safer semantics (at a performance cost) in future releases.
Riak was totally solid when using CRDTs and turning off the insane LWW default.
