Hey Slumpey,
When I interviewed at Worldco, I wore my best suit, and the guy that interviewed me wore a jumpsuit. It was a little awkward, but I didn't know what to expect.
By the way, if you look like a hotshot, (and let them know the fact that you have an interview with more than one firm that day), hence the suit, they may offer you a better deal.
Just a thought.
Chris
P.S. Just let them know you want to be in a group with a good deal, because no matter what the group leader says, they don't teach you shit, so don't sacrifice the deal for the schpeal.