I have been using a Super 23 for about 35 years. It's big and heavy, but does a super job. I've done weddings, journalism, and now mostly artsy photography. The only drawback, in my mind, is it's a little slow as you have to advance the film and cock the shutter in two seperate movements. I have the retracable 100mm lens (required if you want to use the bellows), the 50mm with viewfinder, and the 250mm telephoto. The 250 is the f8, which does not couple to the rangefinder. When I got it, the f5 was really pricey. The lack of coupling really doesn't bother as it's mostly used at infinity anyway.
Close-up work is easy with the ground glass and cut film holders. I often want just a couple of shots, so the cut film is easy, and doesn't waste a whole roll.
I also have an old Heiland/Honeywell flash and bracket to match. Wonderful flash! Done so many weddings with it and it still works great. Other accessories include several roll film backs, lens shades for all lenses, extension tubes, and of course, filters for everything.
The Universal has the advantage of taking Grafloc backs, which allows some more flexibility, and the use of Polarid holders. Otherwise, to my knowledge, all lenses, etc, fit all the Mamiya Press cameras. For more information, see:
http://members.cox.net/gmhsint/mamiya.html