What the previous poster said is pretty much true.
Wharton interviews around 40 - 50% of the applicant pool, and then of that around 30 - 40% get admitted. And since the interview at Wharton is just one piece of the overall application (i.e. it's not like HBS where it's make-or-break), not everyone who gets interviewed has the same shot. In other words, you can have an amazing interview and still not get in, or you can have a run-of-the-mill serviceable interview and still get in.
Good luck
Alex
alex@mbaapply.com
www.mbaapply.com
http://mbaapply.blogspot.com