Corona mills have gotten a lot of bad press over the years, with claims that they are unsuitable for brewing as the give a very poor crush (i.e. tear the grains rather than squeezing them) leading to flavour and extraction problems. The claims have usually originated from either the manufacturers or owners of the more modern roller mills.
But before roller mills (such as the PhilMill, Valley mill and MaltMill) were available for small-scale brewer, Corona mills were the only ones available. Many brewing books had sections on using and adjusting a Corona type mill. Dave Miller's book from the late 80's had a whole chapter devoted to using and adjusting a Corona mill, and he is often quoted as obtaining extremely high extraction rates from the grain.