While I wouldn't advise losing sleep over the idea of a mediocre MCAT score being brought up during residency interviews, some places do like to dig up the past a little bit, although from what I have seen, many do not. Of the 21 places I applied to for general surgery, one sent out a "secondary application" where they not only asked for my MCAT but my SAT score as well.
Although really good test takers tend to stay really good test takers, I have seen people with good MCATs do crappy on the boards if they didn't study, and vice versa; so-so MCATs can still ace the boards. I'd recommend putting a good effort into both USMLE step 1 AND 2- though some people think that Step 2 is not important, on the interviews I have been on so far, Step 2 was discussed more than step 1.
In short, I don't think the MCAT will haunt anyone with an otherwise strong application too badly.
Good luck
-A