I dislike any form of generic, subjective ranking system. Instead I would rather see a table of various metrics for each school (like tuition, NIH $, student:faculty, class size, etc) such as the one listed in the US News database. This way I can cherry pick a few criteria that are most important to me, while ignoring the other semi-arbitrary and often subjective categories.
Rankings are overrated, I'm not saying that reputations aren't important but US News isn't some sort of definitive list of what medical schools are best. The way I've always seen it is this, there are a handful of schools that will REALLY make you stand out... lets say... Harvard, Hopkins, UCSF, Penn, Columbia, Duke.. so on. But beyond that, I don't really think that it matters THAT much. I cared about going somewhere that was well-established. It didn't need to necessarily be ranked super high, but I did care that it was school and program that directors will be familiar with come residency application time.