Hey guys, interviewed here last week. Like others have mentioned, don't worry about the essay. It says on the instructions in bold font that it doesn't factor into admission so I think they're just testing it out this year or seeing what kind of responses they get. You just have to submit it before you leave for the day, so you have plenty of time to get it done while you're waiting for your interview or even after it. It's only about a paragraph or two and you're basically just asked to describe a scene in a picture. Don't stress 🙂
The entire day is very relaxed, only one interview. My interviewer hadn't read my file beforehand (I don't think they're generally blind, but mine was just super busy) and was really, really nice. The interview was very conversational. Though there are a few questions they generally ask of everyone, like "how did you study for the MCAT, "name a challenging time in your life and how you handled it" that my interviewer was asking me from a sheet. But nothing too difficult/stressful.
Good luck to those interviewing as well as those still waiting! Everyone I interviewed with enjoyed their interview and said it was relaxed so don't worry!