From my rotation at HSS, it seemed as if most the residents had rotated there (anywhere from 5 to 7 per year of their 8). however, remember that not all rotators get an interview. Even people who get good reviews and letters from there don't get interviews. At my interview, there were definitely a lot of nonrotators. Not sure how many of them matched this year.

Also keep in mind that after rotating at HSS, when you interview elsewhere, they will ask you whether you are interviewing at HSS as well. If you say yes, then they may think you're less interested in this other program. If you say no, then they may think that you did something wrong, or are not as great a candidate as they originally thought. I may have been reading too much into these questions at other places, but a few flat out asked whether I would choose them over HSS.

I didn't rotate at HSS and still got an interview, as did another member in my class (female) who also didn't rotate. I got the feeling that they do pick students from higher tier schools (like mine), but just a couple. The try to find the best they can from the apps and interview them. My advice, if you're at the top of the pack in your class in a good med school, you may have a good shot at HSS without rotating. The better advice would be do aways at the place you think now you would rather be. People often match where they rotate (I did) and you don't necessarily want to waste an away simply to interview at a good name place that you may not really want to go to or be happy at. Keep in mind that this is only my opinion and may be bogus, but here's my 2 cents.