Follow up question : do you see Rama as being a good fit for applications that /don't/ need Twitter scale? These have simpler requirements, but I feel the integration you propose could still have value there.
It's the ability to avoid the impedance mismatches which dominate existing tooling that makes such a difference. With existing databases, including RDBMS's, you have to twist your application to fit their data models. The existence of things like ORMs help, but they add their own layers of complexity.
With Rama, you mold your indexes to exactly match your application's needs. And you're always just working with objects represented however you want, whether appending data to depots, processing data in ETLs, or storing data in PStates.
That computation and storage are integrated and colocated is another way that Rama simplifies application development and deployment.