Do current students' "review" of you matter in your application? They can. I would not write them off as completely irrelevant to your admissions decision. Last time around, I interviewed at a program where the current students met with the faculty after the social gathering to give their input on applicants. Yeah, they likely do not matter as much as your professor(s) of interest, scores, LORs, etc., but anyone you interact with during the process (whether it be faculty, staff, secretaries, or students) may have some influence in the end. As there is really no way to tell, then play it safe and be respectful to everyone!
Okay, one would think this is common sense, however, I have seen some applicants act extremely rude to those they felt were "not important" in the grand scheme of things. On the other hand, I have also seen current students ignore applicants who did not elect to stay with a current grad student and/or go to the typical social gathering the day before/after. If they're ignoring you, then they may not be putting in a good word for you IF they do have any input regarding admissions.
Please do not read this as everyone must stay with a grad student. Most do understand that there are situations (mentioned in previous posts) where it is better for the applicant to make other arrangements. Heck, even if the program does offer you housing with another student, it is not guaranteed. Sometimes space is limited so you might not be able to stay with one even if you wanted to.
Sooo, if you run into a situation where others are ignoring you, just make sure you hook up with someone else and get yourself noticed (postively, people--please, don't get drunk at the social!). Make sure you interact, SMILE, and be a generally pleasant person. Otherwise, it may come back to bite you in the arse. Someone is always watching and/or listening . . .
G'luck to everyone!