The Leica was very much the old timer of this bunch. Everything is completely manual and after the other two, you have to remember to focus and check exposure. As there is no light meter, I set the X100 to ISO 100, which was the same speed as the Fuji Neopan black and white film I had loaded in it, and checked meter readings for the Leica with it.
Compared to a modern film camera, a Barnack Leica is a pain in the butt to load film. You must trim the leader to a certain shape and size, pull out the take up spool and attach the film leader. The after pulling it out the correct distance, both must be loaded back simultaneously, making sure the film holes align with the take up sprockets.
The big issue with Barnack Leicas is that the built in viewfinder is set up for 50mm lenses only. If you are not using an external viewfinder, there is a bit of guess work involved when using a 35mm lens. While the Summaron is rangefinder coupled, which meant that focusing was accurate, you were never quite sure what was going to be in the picture on the outer edges.
The other issue is with the 35mm Summaron itself. It is very difficult to change the aperture unless the lens is locked in its infinity focus position. Turning the aperture ring causes the focus to change, but nothing else.
My IIIf has the very rare Leicavit baseplate trigger winder. This on its own is worth as much as the camera and lens put together. I had mine rebuilt and it works well, significantly reducing the amount of time it takes to wind the camera on, however it requires quite a bit of hand force to operate and I always worried about breaking it or tearing the film. Interestingly the new Abrahamsson Trigger winder for Leica M7 and MP's is almost a carbon copy of this Leicavit.