Interestingly, many years ago, I worked at a company that tried to build a graph database, but we didn't get very far. Partly, because the hardware wasn't up to it, nor were the software tools.
I''m very glad to see Neo4J has brought this to fruition.
I've skimming over the Neo4J for a while now (since version 3.x), but now I'm actually exploring using Neo4J for a medium sized ontology. I'm not sure where it will go, but my colleagues are interested.
One issue I have encountered, is I am trying to create relationships between two nodes of different types using a CSV file. I can get it to work if the nodes are the same type, but not if they are of different types. The Cypher code executes without error, but creates no new relationships. I tried to post question as a reply in a similar question, but it got flagged as spam. Hopefully that will be cleared and I will get my question answer soon!