Lots of Summars have scratched front glass (very soft flint glass), som many folks have formed their opinions based on scratched up ones. I'm sure that there were also sample variation issues.
It's a nutty lens wide open, but stop down 3 stops, and it's crisp. I have the correct hood, but even with no hood, or just a FIKUS (round) hood, it has not given me flare problems. Great travel lens with a Barnack camera. Only issue is that you need 1/1000 shutter speed if you use ISO 400 film, given the minimum aperture of f/12.5.