Sorry this is a bit late, but good luck to those of you interviewing for R3!
This was my recap post from my interview. I hope it's somewhat helpful! Others have also posted their interview experiences around page 10 of this thread.
mcdonough-2012-calling-all-applicants-120172-180.html#p1032682That being said, my interview was really relaxed and super conversational. I think GT's adcom tries to make you feel comfortable and they genuinely seem to want to hear your story, rather than try to catch you off guard. One warning I'd give (and I don't know if anyone else experienced this): my interviewer told me that a girl with my exact stats applied R1 and was rejected. She didn't say it with any sort of malice or condescension, but now that I look back, it may have been to test how quickly I could positively respond. Just try to keep a positive attitude!
Also, if you're interviewing on campus, make sure you have CASH for the parking garage. I ran into a huge problem with this the first time I visited campus for an info session...let's just say my car was trapped in the president's lot.