Regarding the discussion about how to reject a school among goldielocks, Sigaba, and crazedandinfused. I think that offering critiques of the rejected program should be done very carefully if at all. Personally, I think it works much better to talk about fit or personal preferences, etc. In doing so, you can clearly make it clear why you picked the other school, but coming off as this choice is about me, not about your program having faults is likely to make you seem like a thoughtful person who is making a reasonable decision rather than as someone who is being judgmental or who thinks they know everything about the rejected program (which of course you don't). I also think this approach is more honest--presumably the program you are rejecting is a respectable, good program since that's why you were considering it in the first place--so it obviously has lots of good things going for it and is a great fit for some people, even if not for you.
Re Sigaba's examples, I think there is a pretty big difference between saying this other school has a really important set of documents I can use or better IT or for another example, more faculty that fit with my interests, and saying that some other school has a different "sensibility about diversity." Namely, if you are stating something that is clear and unarguable--documents, numbers--then of course, say it. But I've talked to my advisor's perspective students for several years and talked with him about the recruitment process and I think it is fair to say that the view of a perspective student about subjective things like the "sensibility" of a department about anything (usually gleaned from a day or two visit or a few conversations with a small section of current department members) can be very different than the view of the program, current students, or faculty. Or put another way, I know the reasons I picked my program were pretty accurate and it was a good decision for me. I don't know, though, if the reasons I didn't like another program I visited were accurate or if they were impressions based on the five current students I happened to meet. I'm pretty sure some of them were the latter.
I'm not saying it isn't helpful for that program/faculty member to know your perceptions--it undoubtedly is helpful--but if your priority is building a future relationship with that person, I would word it very carefully. I've seen more than one perspective student provide feedback (and at least one explicitly framed it as feedback) that conflicted with the program's view of itself. Those students came off as snobby and judgmental or maybe naive. They will still have cordial interactions with those faculty members I'm sure, because most faculty members are professional people, but I am also sure, those students hurt the possibility of a more serious working relationship in the future.
