Anyone had any practical experience with this?

I'm somewhat skeptical of the practicality of a graph database backed by a network-connected datastore (as distinct from a graph database exposed over a network interface, ie: neo4j) due to the inevitable latency when traversing the graph.

Also the practicality of scale-out using an ostensibly sharded datastore (cassandra) for a structure that's notoriously difficult to shard meaningfully (graph).