Well, from what I gathered from my interviews, the majority of people I met had taken at least a year off. It just seems like it's more difficult to compete with the extracurriculars you can do after graduating. I applied during my senior year, and got the feeling that it would have been advantageous to take a year off, do some more research or work or whatever. My thinking is that I know what I want to do with my life and don't want to waste any time, but then a lot of people have worked with doctors for a year, gotten published during a year of post-bac research, etc. I'm beginning to feel that the "traditional" applicant no longer applies during their last year of undergrade, but instead takes a year or two off before applying.
I doubt that, with the same application, a med school would look more favorably upon an applicant who took a year off, but a lot can be accomplished in that extra year that really helps.