+1
I also asked this when I was on the interview circuit last year. Professors were definitely impressed. It also has the added value of providing you with really important information. There was one program where I asked everyone that question and almost all of them had the same answer in regards to what the program's weakness was. It was a pretty big weakness to have, too, so I knew then that the program might not be the right fit.
I also always asked about mentorship style. I asked this at every interview and always got really great feedback. I asked this of both the professor(s) I was applying to work with and their graduate students. I would make sure to ask this question in a way that does not ridicule mentorship styles that fall on either end of the spectrum. Don't say something like, "How would you describe your mentorship style? Are you more hands off or do you prefer to micromanage your students?" Conversely, don't say, "Are you more involved with your students day to day activities or do you leave your students out to dry?" (Believe it or not, I knew someone who asked it that way. They did not get in. Shocking, I know).
I think the final question that I asked both professors and graduate students that they really seemed to love answering was "What made you choose to (study at or be a professor at) X University?" This lets you know what both the students and the professors in the program really value. Also, it's kind of interesting to ask professors this, especially the tenured ones. Tenured professors have usually had someone try to poach them from their university at a certain point, so it's interesting to find out what's made them stay (or conversely, if they were poached, what prompted them to make the move). It was actually the way that both the students and faculty answered this question that made me choose the program that I am studying at right now.
I cannot stress how important it is to ask questions. It makes you seem interested AND you gain information that is valuable to ultimately making a decision about where to go.
Another tip: if you know who you're going to be interviewing with aside from your potential advisor, read a couple of their articles. Knowing a little bit about someone's research can never hurt.
A final piece of advice: do your best to come off as a mature adult. The stilettos that you wear out to the club are not meant to be worn with your suit (neither are your Toms). Don't talk about partying/your fly college lifestyle. Don't get drunk at the social events. (This is probably obvious to most of you, but after having spent enough time on the interview circuit, there are some people this will be news to). Your CV can never be so good that people will be willing to overlook immaturity.
Good luck to everyone!