HMS adopted PBL in 1985. They are pretty reliant on it, and actually did a few studies to see how kids in the normal vs new pathway approach did. They did comparably, but the PBL kids were happier, so they switched over.
Cornell switched to PBL around 96, and actually uses a LOT of Harvard's course materials and case studies. At least this is what they told us.
I think HMS uses PBL a bit more extensively, though I have no basis for what I am saying. Both use some sporadic lectures. Harvard has the added cool thing of "blocks" which Cornell kindoff emulates, but theirs are more expansive. HMS jumps to a whole new block every 8-12 weeks. For example, the first or second block of the first year is "body block" and you do your anatomy lab, physiology and some other related things in this 8 week time frame.
HMS is P/F for the first two years.
Cornell is H/P/F for the first two years. The students didn't seem to like the idea of H/P/F at Cornell, at least two students did not like it on my tour, but that is just my experience.