I'm in the same boat as WashingtonDC (including being from the DC area!). I visited Tuck for my interview last week and had the same experience.
My interviewer was a 2nd year and we met in one of the group study rooms. She was great and made the whole thing feel really comfortable. She came out in the beginning and told me "In this interview I am just trying to get to know who you are PAST the words on the page" so she wasn't really looking to trip me up. We kind of jumped right into the interview and she asked all the questions washingtondc listed. However, she was able to weave them into what felt like a conversation. Instead of reading down a checklist of what she had to ask, she just let the interview flow wherever it went, interjecting for clarification and follow-up. Afterwards I was able to ask her questions and chat with her about her time at Tuck.
The whole thing lasted about 45 min but it all felt like a blur. I prepared hard for the interview as I am a basic candidate with a so-so GPA (3.13) so I too knew I needed to kill it in the interview. I felt like it went really well but what do I know!
I'm applying Nov round, so now that I've interviewed, I'm just finishing up essays and won't hear back from Tuck until the decision date in February. Talk about a long wait.