I used the graph part of ArangoDB for a recent project and I appreciated the flexible nature of the relationships between entities (being edges, so always n-n).
For example, my customer did often change its mind about some critical parts of the business logic (and thus relations between entities) and it was a pleasure to update without rewriting too much code.
Also the queries involving many relationships seems more powerful and simpler than in a RDBMS.
Anyway, maybe not an universal solution but, as a web/mobile developper, I can't see the actual limitations with my daily use case.