I'm really not familiar at all with the later metered models, which are the ones you're looking at. Having a through-lens meter would be a substantial improvement over the earlier cameras, which have selenium meters separate from the viewfinder. I can speak from my experience with the IV and the Super (earlier version). They're really quite well made cameras, like what you'd expect from Zeiss Ikon. Leaf-shutter SLRs are quite complicated and I understand quite hard to fix, especially nowadays, but the Contaflexes are probably as good as you're going to get in a leaf-shutter 35mm SLR. So be sure to check the shutter thoroughly -- make sure the shutter opens in the correct sequence at all speeds. If it isn't working right, move on.
As noted, materials and workmanship are top-notch. Solid and well-finished cameras. In terms of handling, my experience (again, with older Contaflexes) is that the view screen is a little dim -- you need to rely on the microprism and split screen for focusing; images don't "pop" into focus. That's of course partly down to the relatively slow lenses. I'm not a fan of the focusing mechanism itself -- there are a couple of knobs on the focusing ring, more or less opposite each other, that work in "seesaw" fashion. It requires a different grip, with basically your index fingers resting on those knobs and your thumbs under the camera. As you note, lenses are limited. I have the 85 Pro-Tessar and it's kind of the antithesis of the compact form factor of the camera with the 45mm Tessar mounted. So it's kind of like having an SLR but limited to the lens options of a Leica M2, which kind of defeats the purpose of an SLR, in my view. Optically the lenses are great, as you'd expect. There is a set of four push-on closeup lenses that provide great versatility, much like a Rolleinar.
Like an Exakta (or a Hasselblad), the mirror is not instant return, so you have to wind the shutter in order to look through the viewfinder. The IV has a Contax-style wind knob. I actually like that better than the Super's stubby rapid wind lever, which is a long throw and doesn't provide good leverage. I think the later Contaflexes have that lever also.
In short -- the whole leaf-shutter SLR concept has limitations, but these are probably the best of the breed. So be aware of the compromises inherent in the design. And there are ergonomic shortfalls in the Contaflex design that you'll need to be aware of. Maybe they won't be much of a drawback for you, but definitely play with the camera and see what you think.
I assume this would not be your only system; it's too limited for exclusive use, I think.
Hope this is helpful.
