I'm an example of successful re-taking. I graduated in '99 with a BCPM of 2.62, or 2.65, or something. My pre-requisite grades were nice and low; I never got an A of any sort, and I think there were more Cs than Bs. I re-took all four of the intro science courses, starting in June of 2004. My post-bac GPA was 3.93, with only two A-s "marring" my record this time.
I sent my AMCAS to 15 schools this year. As of today, I've gotten five interviews and five acceptances. No one ever asked me why I re-took those classes; in fact, no one ever mentioned it to me at all. Of course, there's no telling whether some of those other ten schools did just that and decided not to invite me for an interview.
So it can be done, but I would recommend you work your butt off and do everything you can to earn As while you're taking them. Otherwise you're just going to waste your time and money.