We are using AWS Neptune in building our marketing analytics product. What I have realized is that it has best of both worlds, the querying power of SQL databases and schemaless functionality like nosql databases.
Whenever I read mention of Neptune, I feel obligated to mention Blazegraph, which Amazon based Neptune on.
As I've shamelessly advertised elsewhere in these comments, Blazegraph is in the early stages of a fork and/or reboot, as Amazon's acquisition severely hampered progress on the open source project.
