Rebecca
As a freshman, many of your technical classes will be large lectures with small recitations. This may worry you, but don't let it. There is no need to have a small class for multi-variable calculus, and your TA will help you along the way. Some introductory class professors are available in office hours etc, but most students get help from TAs. As you get older, you start having smaller classes, and can get to know your professors. That is up to you though. You need to put in the effort to build the relationships that will serve you while you are still in school, and once you leave.
MIT has a very collaborative atmosphere. In my department (civil engineering), for example, students are required to work together on problem sets, projects etc. to imitate what the work environment will be like.
Studying is everyone's main activity. You can make time for other things if you are organized, but this is not a place to skate by.
Harper
It sucks. You learn to love that it sucks. You learn to party on Thursday night even if you have to stay up till 5am to finish that pset.
Sleep. Social life. School work. Choose two.
Piper
Freshman classes tend to be largest since everyone's required to take certain intro classes, and from there classes shrink. The nice thing is that the professors are only an email away. They're all required to have office hours, so you can see them in person. They're usually willing to talk before or after class, too. If you put in a tiny bit of effort, you'll be fine communicating with profs. Students are always having intelligent conversations, though not necessarily about a class because people read stuff about all sorts of topics and have tons to share. The nice thing is that since we don't have any class rank or graduation honors, competitive people are only competing against themselves, seeing how much they can push themselves. I haven't experienced any backstabbing nature like at other schools - everyone collaborates because that's what you have to do to survive. It's tough here because any given class will make you go more in-depth than you ever thought, so you'll learn tons just for the sake of learning, more than you'd probably need in a job. But in turn, you end up prepared for anything in the future.
Gina
There is no better place than MIT for math and science. I love most all of my engineering classes. Most of the professors are friendly and accessible. Everyone here wants to see you succeed so you can always find someone to help you out if you're having some trouble in a class (which is bound to happen more than once).
What I really like is that most students here foster an environment of collaboration rather than competition. Classes are insanely hard, so most students work together to get through them. We have group study sessions and our teaching assistants will bring juice and donuts for long office hours.
I also feel comfortable talking about classes outside of class. People here are genuinely interested in what other classes are studying. It's normal to overhear conversations about a student's lab project building a robot or extracting an important biological molecule. You can talk about things here that your friends back home would never understand.
Nico
Students study more than anything. It is competitive. Classes are interesting. I know of no professor who knows my name as I sit in a big lecture hall. The professors that do know my name know me because of other encounters not related to a class. MIT academics seems to balance the goals of learning for the sake of learning and learning for the sake of expanding one's career toolbox.
Chris
One thing to change about MIT is to loosen up the requirements for classes, because that would allow for students to actually take classes that they enjoy and are interested about.
Carrie
Your academic experience at MIT depends a lot on your major. I started out as a Course 1 (Civil and Environmental Engineering) major, and the classes were extremely small, though they were sometimes frustratingly disorganized. When I switched to Course 5 (Chemistry), the classes became much larger, but the lesson plans were well thought out, and I knew more of my classmates. MIT is too large, in general, for your professors to know you if you're not going to make an effort. You can definitely slip by unnoticed, or you can choose to be extremely involved in your department - organizing events, doing undergraduate research, and spending a lot of time asking questions and becoming familiar with your professors. Like many other aspects of MIT, its mostly left up to you; there is a lot of independence and responsibility - no one is going to look after you, which is usually a good thing.
KC
I spend a lot of time on homework, and I'm not beneath copying my friend's problem set if I'm still not done at 3 in the morning, so I spend less time than most people. Maybe I spend 18 hours a week? I think MIT's core required classes are good - then everyone gets a feel for all the sciences - if I hadn't been required to, I wouldn't have taken chemistry, but it's good that I know it now. Also, it's good to require so many humanities, because then there are more choices - then I can take a variety of classes that are not math/science but still not have to take English - I took anthropology last semester and now I'm in linguistics. I have not gotten to know any of my professors, but I've still pretty much only been taking introductory courses, so I don't think that's representative of classes that are smaller, in my department. I'm majoring in civil engineering, which has a pretty small department, so I'm confident that I will get to know my professors. But I do learn most of my interesting math/science tidbits outside of class, in conversations with my friends!
Lisa
It's hard. Really bloody hard. You'll be studying 24/7 here. Within your major you'll be well known to your professors and TAs in and out of the classroom. It's a great education and definitely prepares you for either a job or continuing higher education.
Casey
Academics are very rigorous here, but MIT pays enough attention to students in terms of making professors and TAs very easily accessible. Classes cover a variety of topics so that students can choose to take courses that they want to know more about for learning's sake, or purely for the transcript.