Speaking from my seat in the back of an auditorium with about 200 students, I think that the large class size is actually more good than bad because...
-like you said, more opportunities to meet people, more people doing cool things when you don't want to study, etc. Coming in, I figured that with 200 people I was sure to meet at least 4 or 5 that I could get along with.
-It's easier to have more, and more active, student groups. For one, there's someone interested in everything, so there will be an interest group for every specialty. Also, those groups will have the manpower to actually do things without the same people doing all the work (unlike my small high school).
-If you want to just blend in, you can. On the other hand, in terms of "getting lost in the shuffle," I don't see how being in a class of 200 is any different than a class of 100. You're still gonna be in a lecture hall, and a lecturer is no more likely to learn your name in the smaller class. If you want to ask questions after class, you still can, but remember that a lecture is a lecture (ie. usually not all that interactive) now matter how many people are there. Your small groups will still be small, there will just be more of them.
-Grading--your issue kinda confuses me, probably because I'm not sure what a "4 interval scale" is. I'm guessing that any school that grades its students against one another does so based on percentages, so it shouldn't be any harder to honor at a big school. In fact, speaking in raw numbers, more people could "beat" you and you could still honor. In general, I don't think this would be an issue. Oh, and you shouldn't be working for the grade, anyway, right?
Anyhoo, that's my take. It seems to me that this is something that really concerns people that are applying and I don't really understand why. Hopefully some of what I wrote makes sense. I'm sure there are folks on the other side of the fence that will call BS on all of it, so sort through stuff and figure out how you'll be most successful. Good luck.
