Jason,
Maybe not necessarily better for digital, but if you are going to continue production of one body, it will be the most flexible one... as mentioned, TTL, capability of adding a winder (some backs for some reason require auto cocking-I haven't researched enough to find out why, or maybe they/it was only designed for the 553ELD, I forget).
As far as sync cables go, I would assume you either got a Y-plug or cable with the back, or there are 3rd party products to allow you to split the signal. A little Y-plug comes with the Macro Flash, so if you already have one of those...
Until there is a full frame back, quite a bit of the FOV of the 30mm lens (Hasselblad or Arsat) will be lost and you'll have a highly distorted 40 to 60mm lens depending on the chip's size. It may be cheaper to get a decent film scanner if you do not shoot too often, and you won't have to "crop" your wide-angle lenses in camera.
Taras