I am in the midst of interviewing for a general surgery residency position right now. As far as competitiveness, it's not as difficult to match as it was several years ago, but I think the numbers are up from last year. Columbia had over 850 applications (for five spots), U Michigan over 600.
For USMLE scores, it depends on what programs you are aiming for - if you want to go to Mass General, you should at least beat the mean. But if you want to train at less competitive hospitals, getting the mean should be fine.
I think getting honors in your surgical clerkship is very important, but if you don't, it doesn't mean you won't match somewhere.
USMLE scores, grades, and letters of recommendation are all important. From my experience, I don't think the actual interview is that important. I had one program tell me that I was high on their ranklist, and I hadn't even interviewed there yet.
