My vintage lens collection is growing by leaps and bounds. I have gotten some good results from some of the lenses, and in some cases I find that they equal or exceed a number of currently available (newly manufactured) lenses.
However; not every vintage lens can be used safely on every camera. I think the old film cameras must have had larger registration distances between the mirror and the rear of the lens barrel. Certain lenses, when they are focused at some point in the direction of infinity on the focus ring, protrude from the rear of the lens mount.