I am currently in my 2nd year off. I spent the summer after graduation continuing my research and volunteer work. Then i took 3-4 weeks off to backpack through Europe with friends (something i don't think i'll be able to do anymore with time committments, etc. i'm very glad i did it, plus i had a stressful experience that i can talk about in interviews) Following that, I've spent the past year at the NIH and immersed myself in brain imaging research, another experience i don't think i would have gained elsewhere.
It hasn't affected my admissions process at all; in fact, it gave me more time to study for the MCAT and improve on my past score. Plus, on my interviews, I've met a number of people who've taken time off to do other things (MS's, MPHs, work, etc). The experience, in my opinion, is invaluable, especially if you continue to do things that will enhance your application.
Good Luck!