In 4.01 we added support for doing a deep update by doing a PUT against an entity with an inline set of objects; the semantics are that, at the end of the operation, the entity contains exactly the entities specified in the payload; any entities not specified are removed (and, for containment or if an integrity constraint exists, deleted).  This is the same semantics as doing a PUT with a nested collection of primitive or complex types.

We do not, however, currently support the same semantics against the path that specifies the same collection.  That is, a PUT to customers(1) that contains nested orders replaces the orders for customer 1, but a PUT to customers(1)/orders is not currently specified if orders is a collection of entities (though it is if orders is a collection of complex types).