I just wanted to respond quickly to a post Marty made about my initial use case.
The directories themselves DO NOT have to have the same schema. It's
very common case where OVD is used to provide a single point of contact
for both an AD and a Sun Directory server. This is a popular deployment
model where staff data is in the AD server and customer data is in the
Sun server.
And you can do all of this using a nice point and click interface.