Hi Craig
Compared with SQL or others storages mongodb (specially the .net driver) provides a much richer functionality.
Due to this fact, the need/benefits of an ODM are not as big as it is with the relational dbs and there´s a gap in the .net ecosystem for mongo db.

There are still some functionalities that I really miss for an enterprise application, one of the main one is caching. In most cases there´s catlog data, definitions that can be cached reducing the amount of queries sent to the DB enormously.

I understand this probably should be in a contrib space, but I don´t see any active project that could deliver this functionality.

Also I saw in one of your conferences that you intentintionally did not resolved the mapping between collections (Foreing keys in relational DB). I understand that in some cases yes, denormalizing data is the right answer in mongo, but not always.

The fact that we have a full Repository pattern with a NHibernate backend repository with all relations mapped as objects, whithout this support makes the almost impossible the migration.

The new conecpt of "Few to many" should be an array of objects, but there are many cases of truly many-to-many or one-to-many.