I'm on the 5 yr mark, and I've got an excellent reason. $$$ School cost a lot of money, I don't come from a rich family, loans are not an ideal situation and if I can put them off, it's what I intend to do. That and I flopped around between majors for a while, but who doesn't do that? Taking more time to graduate in over 4 years is becoming more common.
I mean, unless you're in school for 17 years retaking the same class over and over and over, I don't think it'd be an issue, people have uncertainty, people have money issues (especially in this economy), people have personal emergencies, people live life, I don't think it's unreasonable for someone to go off track a bit, especially if they are otherwise well-qualified. But that's just me.
Bottom line, it is what it is. You can wish you'd done this, wish you'd done that, wish everything had gone according to plan. Wish you had a plan, wish you hadn't made any mistakes, but you can't change any of that. All you can do is do the best with what you've got. And again, I could only hope schools would realize that not everyone is able to flawlessly accomplish the difficult task of becoming a doctor, or college in general.