Wow, surprised so many people here are saying this is such a minor issue. Almost had a very major accident today because of this issue. Happened to me twice since I got the car, both times, when pivoting from accelerator to brake pedal when I needed to stop in a hurry-- well the car didn't stop like it was supposed to and I had to swerve out of my lane to avoid hitting the car in front of me. Never really experienced this in any other car before. And I'm a little bit worried about the issue as it only seems to occur at the worst possible time for me. I would like the accelerator to just be flat out disabled when I press the brake pedal as I would never want to have both going at the same time anyway... Surely that could be a software switch?
It's interesting that the sentiments on this are so evenly divided: roughly half of the commenters saying it is a big deal and half saying it's not a problem. It happens to me quite regularly and has so far been no more than mildly disconcerting, but I can appreciate that in a panic stop you would absolutely not want to mistakenly press both pedals. I've experimented with placing my heel in different spots, but the placement that seems to eliminate the problem is not my default, and feels awkward.