Also got invited to interview. Got the email at 2pm.
I was there for a class visit in November, and people were pretty consistently in business casual. It looks to me, too, that the panels they are offering on the interview day are the same ones they had on the visit day I attended. I definitely recommend sitting in on a class if you can. They had us introduce ourselves and say what food we could eat every day for the rest of our lives if we were stuck on an island (I said mac and cheese, if you're interested). Everyone was incredibly helpful. I signed up for the first Friday interview I could get to get this whole process over with. Good luck to all of us!