I have OM and PenF lenses, bought new in 1969!
I use the PenF 40mm F1.4 quite often on my PM1. The IQ of this lens is excellent, color and contrast as well. Amazing considering the coatings of that time, and no color cast. As good as any new 4/3 or m4/3 lens, and better than most OM's. And it's tiny, very suited to a Pen or OM-D. I had it cleaned and refurbed by a professional recently, and its like new.
But they are expensive, and unless you are into MF, and don't mind taking your time, the latest lenses are more practical for most.
This was taken close, so exaggerates the lens size