I found that study interesting, but I think there's one problem with it that is difficult to address. Using an appearance in the majors as your measure of success biases the results toward high draft picks; if someone is the first-round pick, teams are much more likely to bring them up, at least for a bit, just because they were a first-rounder so there must be something there (Adam Johnson). That doesn't make them a real major league ball player. The same player who was a 14th round pick never gets the call. At worst, all the study shows is that clubs are more likely to promote top picks, not that they make better ball players. I don't think the bias is that severe, but I think it does put the value of results in some question.