Tugs,
It is my understanding that Southwestern (Dallas) interviews all of the students who rotate there. I too was a mediocre candidate, went there and busted my hump. This was well received. (and you WILL bust your hump there). Also, my home program (CWRU) interviews all rotators. I will be at the University of Kentucky (hence the name), and it was my feeling that they interviewed all their rotators as well (plus it's a great place). Overall though, I think that a low-drag, high-speed performance at ANY program (except a few) can definitely help you out.
Just a word of note, I would stay away from Vanderbilt: I did a rotation there, busted my gastrocs, got a letter from the chairman and STILL... did not get invited to interview.
But that's just me.
Best of luck and happy hunting.