Overwhelming but amazing

Introduction
So now everyone knows NYU's heralded as America's "Number 1 Dream School"...and with good reason, for sure. Going to school in Manhattan is incredible; there's always something to do or see, between museums, theater, concerts, street fairs, rallies and protests, shopping, sightseeing, and aimless exploring. And while all of that is amazing and makes for a college experience totally unlike the one you might have at a rural or suburban school, it's definitely not for everybody. First of all, the school is enormous, and not just in terms of the undergraduate student body (20,000+). The "campus" consists of sporadically placed buildings all over downtown Manhattan. There is a sort of "hub" of 5 or 6 blocks from West 4th up to about 10th or so that is undoubtedly the NYU 'hood, but the school is integrated completely with the city. And with Washington Square Park (mostly) closed off for renovation, the closest thing we have to a "quad" is also gone. With so many kids, hangout spots, dining halls, dorms, etc, it's veryyy possible to meet someone great who you'll never see again.

Campus Life and Social Life
This is difficult to answer, because the campus is basically indistinguishable from the rest of the city, so in essence, NYU's social/campus life is whatever you want it to be. Since coming to NYU, I've hung out with NYU students and non-NYU New Yorkers alike-- because the school and the city are integrated, you meet both groups in the same settings. There are the typical dorm parties, but more often people go out on the weekends. At a school this big in a city this big, you can pretty much do whatever you want with people who you like. I'd say the drinking is about average, maybe a little more intense. There's really no need to get a fake ID; it's expensive and illegal and not worth the risk because so many liquor stores and bars in New York don't card. If you want to drink and party you will be more than able. Some people frequent clubs, although I'm not a big fan, personally. One suggestion, though: avoid the "NYC nightlife" facebook event invitations you get as soon as you join the NYU network. They're typically lame and sleazy clubs and bars capitalizing on freshmen's naivete by charging enormously jacked up covers and way too much for crappy drinks.
The Greek life is incredibly minimal. I'm a freshman and I don't know anyone who's in a sorority or fraternity, although I do occasionally see them holding fundraisers and whatnot.
There is a staggering number of clubs and organizations at NYU, catering to nearly every imaginable interest, hobby, faith, ethnicity, race, political persuasion, career path, etc etc. Some clubs notoriously attract hordes of members-- i.e. the Young Democrats.
One aspect of the NYU club experience that evokes both love and hatred is the school's tendency to absolutely hemorrhage money on student activities. Of course, we don't know exactly how much money (see "In Closing"), but it's enough so that if you keep yourself signed up to some club mailing lists and facebook groups, you'll never go hungry thanks to regular free club food.
As far as sports are concerned, the joke is that NYU sports are virtually nonexistent. More accurately, they're existent but just not a big deal. I've been to a couple sporting events because my roommate is a cheerleader and they're refreshingly lowkey. If it's important to you to have the typical college experience with homecoming football games and rival schools, NYU is simply not for you. While the competitive sports scene is minimal, there are two gyms on campus open to students. Advertisement
Academics
NYU is competitive during the admissions process, and it's competitive once you get here too. I'm sure this depends enormously on what you're studying and who your professors are, but the workload is generally intense and can be very overwhelming at the beginning of first semester. I'm in the College of Arts and Sciences, in which students have a multi-faceted core curriculum to fulfill called the Morse Academic Plan (MAP). Freshman year, CAS students generally knock a couple MAP classes out of the way (Natural Science, Quantum Reasoning, a language proficiency requirement, Conversations on the West, World Cultures, Writing the Essay, among others). As a freshman, you pick classes last and it is incredibly frustrating to not get exactly what you want. But fear not, because every other freshman is in the same place.
The Bobst Library at NYU is incredible. It's open twenty-four hours a day, seven days a week and it's spectacular, a total sanctuary. Wifi is available in almost much every NYU building (note: not in dorm rooms, although in dormitory lounges and penthouses) so you can park yourself in Bobst or the Kimmel student center or a dining hall to do your homework.
I haven't had a bad TA experience yet, although I've heard horror stories about the disgruntled TAs who don't really care about the class and grade arbitrarily. A couple years ago the TAs went on strike because NYU refused to recognize their union. NYU never met their demands, and eventually they went back to work. Hence, there is some truth to the disgruntled TA stereotype. In the larger lecture classes-- and there are quite a few of those-- your weekly recitation with a TA pretty much makes your grade.

Student Body
People are quick to put broad stereotypes on NYU students-- predominantly white, wealthy, upper-middle class, Jewish, gay, etcetera. But in truth, the demographic breakdown is impossible for one student to assess because the student body is so huge and scattered. Smaller communities form, but at the end of the day, there really is no all-encompassing "NYU community." I like this, personally, because it feels less like I'm in college and more like I'm an adult living in New York City. However, for many NYU students, it is a source of resentment.
Another thing that is important to know about the student body is that for all its diversity, it can feel almost politically homogenous. In my suburban Connecticut hometown, my personal stance bordered on radically liberal; at NYU I feel practically moderate. Don't misunderstand: conservative and Republican students are here and vocal. But if you're an outspoken right-winger, be prepared to encounter some hostility.
Of course, confrontation is a favorite pastime of NYU-ers. Rallies and protests are regular events for such student groups as the Campus Anti-War Network and Students Creating Radical Change; the occasions range from speaking out against the US presidential administration to demanding policy reform from NYU president John Sexton. Sure, it can feel a little forced and over-the-top, but I would so rather be at a school where student activism runs rampant and loud than at a school full of apathetic kids who don't care about anything.

In Closing...
NYU is so big and multi-faceted, and this can result in a lot of bureaucratic bullshit. It takes a long time for change to occur at the administrative level. One of the biggest complaints coming from the student body this past year was about the school's refusal to make the budget transparent. This is one huge problem that I have with the NYU administration; we're paying a lot (or racking up a lot in student loan debt) to go here, and I want to know exactly how my tuition is being broken down.
Every undergraduate student in CAS gets an academic adviser, and I am always surprised by how personally my adviser seems to know me, even though I'm one of quite a few students he advises. As an undergrad, you can feel a bit like one tiny fish in an enormous ocean. Getting personal attention is possible but requires more effort here than at a smaller school.
One thing you definitely won't hear on the tour is that NYU generally isn't held in the highest regard by the Manhattan community. NYU is a big landowner in the city, and NYU kids can be a pain in the ass for locals-- especially when we're drunk and loud and walking 5 abreast on the sidewalk. NYU has also imminent domained the heck out of some people living in the Greenwich Village area in the past couple decades. It doesn't have the best reputation, so be ready for the occasional snarky comment from a local. However, for the most part, NYU is such a critical part of the local economy, you feel as much a member of the community as anyone else.