Actually, my pre-med advisor said that med schools may not like to see a candidate with a "perfect" academic record, because they haven't shown that they're able to deal with adversary. Someone who's used to getting perfect grades may not be able to deal with getting one grade that is less than perfect. Med schools don't just care about the numbers but care what kind of student you are and how you can cope with a "failure" (and yes some of us consider one B a failure).
So in short, a 3.8 or 3.9 may actually be BETTER than a 4.0, as crazy as it sounds...
If a perfect GPA were THAT important, there would be at least some med schools where the average GPA is a 4.0 or VERY close to it - and there aren't.