Apple most likely purchased the screens all in one "batch" so the possibility of "bad batches" seems unlikely to me. I feel LG made these solely for Apple, as info regarding these screens doesn't even exist, even with a model # search. I also doubt Apple cared enough about the issue to scrap the first order and demand a second revision out of LG. ($$$)
Thus, I feel that anyone claiming a perfect screen needs to find someone in person who can tell the difference and have them look, too. Otherwise I will consider it a false negative until otherwise proven (pics, video?). Now, in the OP's case, "another guy in our college" means that you have SEEN the yellowing yourself or is it just by word of mouth? If it's the former then I'll ask you to look REALLY hard at yours again, or have him look for you. If it's the latter, then I can't trust that yours is actually fine at all.
Maybe I'm just being cynical, but I find it more likely that they all exhibit this issue (to some extent), than 90% DO, and 10% magically DO NOT... I feel that maybe the "DO NOT" are just false negatives.
Despite my cynicism, I'm keeping this for now, and will ask for a screen replacement when I finally see a 27" with my own eyes that does NOT exhibit the yellowing. I haven't yet, and I don't know if I will until Apple orders a new batch. I lucked out in every other regard, no DOA, no messed up power button, no cracks, no dust, no dead pixels, no flickering, no excessive HDD noise... and all of these issues are far less acceptable to me than a slight yellow hue, so I'm not going to be stupid and gamble for a replacement.