Indeed, Val. I attended a school that had pass/fail (and high pass) for the first semester. This was done in recognition of the problem that many of us parents on this board are working hard to avoid: kids entering after acing AP and honors classes without having to work at it, suddenly hit these difficult university classes faced with the realization that they lack basic "how to learn" skills. My room mate went through a painful process of trial and error figuring out how to get all her work done, how to ask for help, and figuring out how to study for a test for the first time in her life. Instead of having a spotty first year transcript, she had passes.
We had a lot of support in the first year, both from the college and from peers, but still, many students did "ITR" (ineligible to re-register, aka "invited to retire"). When I was deciding between MIT and the school I ultimately attended, they seemed very similar in the pass/fail system, as well as in ITR policies.