I dunno. It might depend on which NoSQL folks we are talking about. Certainly the array-native database folks are not even close to the relational use case.
I also think the best way to look at NoSQL is that it is just a further development on Stonebreaker's bottom-left quadrant database division--- object databases.
The more I get into it, the more I am astounded with the power of PostgreSQL to take over all these workloads on the low-end and more.
But in this case at least you are using PostgreSQL outside of anything even remotely purely relational. It is at least object-relational, and often key-value-id (like hstore) or document store (JSON or XML).
The power of PostgreSQL occurs from the power to ignore the relational model and take other approaches when it is helpful.
I also think the best way to look at NoSQL is that it is just a further development on Stonebreaker's bottom-left quadrant database division--- object databases.
The more I get into it, the more I am astounded with the power of PostgreSQL to take over all these workloads on the low-end and more.