If nothing else, the Shorty McForty is an awesome body cap.
Pro tip: mount the Shorty McForty, take off the grip (if you have one), turn on Live View, and you've now got the ultimate party camera. Not many people will realize it's the IQ / low light monster it is, and just think you've got a high-end point-and-shoot. Put it in green square mode and hand it off to people and they're still not likely to realize it.
Of course, there's also an awful lot to be said for the 400 f/2.8, as well....