The part that interests me most, and that has the wider implications in the long run, is the atompub / gdata part. Facebook can make a proprietary api "more truly open," as Mark Cuban says. But that just becomes the means for more easily having "third party" support for an OpenSocial "gateway", if you will, for Facebook.
There are all kinds of "innovation happens elsewhere" implications of the OpenSocial atompub / gdata part that overshadow "gadgetry". From the OpenSocial docs...