I don't own a Leica, but have a Zorki 1. It doesn't even come close to what my IIIC has in looks and personallity, but then that's where they are the least alike anyway. As mentioned before by many others, you can't beat the Retina viewfinder, especially the IIIC, with the framelines for all three lenses and it's larger viewport (which will also take a right-angle viewer). But I have issues with the ergonomics of it.
Not much to grasp with the right hand, the EV system of exposure with it's hard to change locking lever, and Heaven forbid you should forget to reset the frame counter. I don't consider the interchangable lens elements as any kind of advantage when you have to recalibrate your focus with every shot. And why a plastic hood? I wonder how many of those got crushed in someones pocket. Must have been a conspiracy with the plastics suppliers for Kodak to go that route.
But the IIIC is such a lovely camera, even with all it's quirks. If the meter was working on mine, I would probably shoot it more, but I have other choices. Sure, the Zorki doesn't have a meter, but it sure is easier to use Sunny 16 on than the Retina.
I'm thinking of letting the old girl go, since I'm not going to be able to give it the work it needs to keep it happy (you reading, Keith?). But it was one of the cameras I had lusted after for a long time, and I came across mine in such a surprising way. And did I mention it's just gorgeous to look at, and to hold? And the sound of the shutter! Sigh...
PF