I'd like to take a stab at this.. and play devils advocate for the opposing perspective to the points (valid as they may be) that SLC made. Keep in mind, these come from perspective being in the situation of a high GPA/ mid-low mcat category...
For me, there are a variety of factors that contributed to having a GPA that doesn't come close to correlating with my MCAT score. When I was asked about this in most my interviews I was honest and straight-forward. I feel like my high GPA has proven I have the ability to take the long-term rigors of school and stay focused on it. The main reasons for my poor MCAT are reflected in both where my priorities were while studying for the MCAT and with the way I went about studying for it.
1. I didn't prioritized my mcat prep as I was studying last spring while balancing many other commitments. This isn't an excuse but it is an explanation. I made a personal decision to stress my personal life and college course work rather than the mcat prep and this didn't cut it for me as reflects my less than impressive mcat score. However, if it had ended up being a hindrance to my app I would have studied more intensely and hopefully rocked it
Luckily... I had a handful of acceptances, more interviews than I can afford to attend and I am happy with how things worked out
2. I studied the wrong way, flat out. I prepared in a similar way you would for regular college class, spending what time I had going over the details of the science. What I should have done was practice, practice, practice problems. The MCAT is its own beast and as such, you do need to know material but not in the detail you would in a class. It's about learning to use what knowledge you have and problem solving. Much of the MCAT can be reasoned through with less than a full theory of knowledge of all the science memorized coming in.
I explained these things in my interviews and let them fall where they may. It was never used as an excuse but rather was the honest reflection on what I did and what I could do differently. I am using this potential negative as an opportunity for learning and my interviewers seemed to appreciate that.
I agree with SLC that sometimes the GPA/MCAT discrepancy can be a red flag but you need to know yourself and figure out why that problem exists. Ultimately you need to know why because all the boards are "standardized" exams and if you have a problem with them, you need to know how to fix your issues early on because it's not going to magically improve in a few years.
In all fairness though too, I feel high MCAT/low GPA can be a sign of problems too. GPA is the result of long term patterns and trends seem to be more an indicator of a student than overall GPA. I don't believe a high MCAT score proves your ability to handle becoming a physician any more than the reverse because while it may indicate you have the brains to handle the science it begs asking why your GPA wouldn't reflect the time/dedication that that score may show the potential of. This may not be the case with non-traditionals but just again, just an opposing question.
I think my ultimate point is, you need to do some serious reflection and figure out your own situation and why you are where you are, with a unimpressive MCAT and high GPA. You need to know because schools want to know and also because by fixing a weakness you can improve your chances of becoming the best possible physician.