Echo RVD re: Wharton EMBA attire: do the suit if you've got your interview that day. If you sit in class (and you should), there will be other dorks like you in there all dressed up, and the students themselves were in your shoes not long ago.
I did the interview/visit in the same day. The original instructions said business casual, the final instructions they send the week of your interview said business or business casual. From my hotel room on the road I winced a bit.
I had planned for good business casual because I was coming in from a long week on the road. I hadn't brought a suit with me.
Of the 6 or 7 fellow interviewee/class visitors I meant, only myself and one other guy weren't in a suit. I fretted a bit in the waiting area, but whatever, I figured they weren't going to take me or not take me because I wasn't wearing a tie.
But don't listen to me, rock the suit.