Over the last month and a half I received responses from most of the grad schools I applied to: I was accepted to the chemistry departments at Berkeley, Stanford, and Caltech, and have been invited out to Scripps for an interview. The professor at Scripps who called me to share the news said that "interview weekend" was a formality and that I would almost certainly be admitted. I'm not sure if this is true for all of the interviewees or if some of us will be denied admission after we visit. My instinct is that it's the latter because the Scripps professor tried to sell me on the school, indicating that he will probably put in a good word for me when it comes time to formally extend admission offers. However, not having had much contact with professors at the other schools I was admitted to, I don't know to what extent selling a prospective student on the department is standard practice (my only other data point is MIT's chemistry department, where I heard from a friend that the prospective students were taken out for a very fancy meal in Boston's north end last year).
I still have not received word from Harvard and MIT, which are the other schools I applied to; however, as is probably obvious from the list of schools I applied to, I'm eager to be in California. At this point, it's unlikely that I would want to go to Harvard anyway; I recently heard that the professor who I was most interested in working with there is no longer taking graduate students. And of all the schools I applied to, I hear the worst things about MIT in terms of work hours and grad student morale (although there are a couple people I'd be interested in working for there, who may not have reputations as slavedrivers).
For now, I'm not really sure what to expect from all of the meetings I'll be having with professors at these schools. I'm meeting with around six professors / research groups at each school, and in most cases that number is higher than the number of groups I'm truly interested in working in. So, I'll be meeting with people whose research I don't know much about. I'm sure these interactions won't be tests of my knowledge of their research programs, but it seems like at least a familiarity is in order. I've read recent papers of the groups I'm most interested in working in, but for the lowest professors on my list, it's hard to motivate myself to find out more about their research when I could instead be spending my time reading about something I'm more interested in.