We just added a lot of functionality to our query system, but it is very much a work in progress. Making it easier to create queries that represent relationships is definitely on our task list.
For some tasks, this is undeniably true, but for most business problems I think this is just not the case. The profound irony behind this is that schema-less document stores wind-up being so much less flexible due to them being inherently very denormalized.
The good case for document stores is:
1. You have data that really is a blob independent of having relations 2. You need high-performance or map-reduce (Riak, Dynamo, etc.)
Those two use cases are really rare in the real world. For most people there's a huge amount of code that leans on RDBMS strengths such as:
1. Integrity constraints 2. Very flexible ad-hoc queries. 3. Decades worth of work on tooling to mitigate rough edges, and solve tough problems that have come up before.
For our particular use cases, we think that document stores are a better fit, but I am not arguing that document stores are universally easier or better.