Med School is a different animal than college, law, business, education, graduate admissions. In college (arguably), where you go is relatively important. In law (definitely), where you go is crucial. For the others, most applicants tend to pursue schools with particuarly strong departments in their field before considering "overall" rank.
But in Medical School, the overarching goal is to get in, period. So there's been much less fanfare and bickering over which school falls into which "tier." It's also more difficult to hierarchically organize medical schools because all of them are subject to rigorous standards for accreditation and must produce competent, able physicians.
With that said--I think going to a "top 10" is widely regarded as a big deal, and after that going to a Ranked school is admired, and after that getting in ANYWHERE is an accomplishment. So if you're looking for "tiers," I would venture to say that the three are Top 10, USNEWS Ranked, and Everywhere else. At the top end there seems to be an inordinate amount of positive publicity for Harvard and Johns Hopkins (though the quality of education offered there is debatably no better than many, many other schools), and at the bottom end you might want to do some research on schools which are having trouble with accreditation and/or finances.
If you're looking for a good balance in your choice of applications, buy MSAR and use the GPA/MCAT as an index. Put most at or slightly above your stats, a few below, and a few above.
Z