I also use the Zenitar, and found it a lot of fun to shoot. I have not had a problem with OOF images, but I use it with a Canon F-1N, and just rough in the focus fast.
This lens is around $100... which means you CAN play with it, and not have to mortgage the farm to buy it. It seems to be very adequate in both sharpness and contrast, and the color rendition is pleasant. A nice buy for the money. Mine has a standard Pentax screw mount, and I use it with the Canon Adapter P.
Just a thought, what about adapting this to the Canon 7s, or the Leica M3 with an appropriate adapter? Anyone try this? No real need for a finder... just hold the camera straight and level, and figure WIDE, BABY, WIDE.... 180 deg. wide.
Might be a project for the weekend...
Harry