They sent me a letter that said "We are impressed with you, even more so than all of the people who we send a letter to saying that we are impressed with them when we really don't mean it." But I failed to get the letter saying "You are among the 31 most impressive applicants so you have been ranked to match." Without that letter, I do not get too excited.
Of course I am kidding, but I did get the generic "impressive candidate" form letter as well. I have a feeling that a lot of people get the same letter. My thoughts are that they send it to most interviewees, so it probably doesn't mean too much. It definately is not a bad thing to get it, but I wouldnt go ranking them as your only choice or cancelling interviews at any other programs you may be interested in.
They play games just as much as the applicants, and I think it is best to be humble and underconfident in this process rather than being naive.
Best of luck and I hope you guys get your first choice!