Best. School. Ever.

Introduction
Every Ivy is going to give you a great liberal arts education...duh. But Penn is special, because not only can you do history, econ or Chinese, but you can also add some marketing, negotiations (learn to screw like Penn alum Donald Trump), management, or other skills to help you deal with business (and this isn't just for Wharton students; anyone at Penn can take these classes). You just can't do that at Harvard, Yale, or Princeton. And let's be honest, unless you're in Communist enclaves like North Korea or the average college campus, life is going to involve interactions with business, so it's for the best.
If you do not have a lot of individual initiative, Penn probably isn't for you. Nobody will hold your hand in a school of 10,000 undergrads, and if you don't take the initiave in making the most of your education, extracurriculars, and friends, you will fail. If you need your hand held, if you want the teacher to give you a hug, if you're afraid of poor people, or are otherwise a wuss, go to a liberal arts college.

Oh, and Philly is great too. It's big enough to be a REAL city but not big enough to suck life away from the campus

Campus Life and Social Life
Penn embodies the work hard/play hard cliché. Penn is one of the few schools in which there is a ton to do on campus and far from it. You can go to a swank downtown restaurant, downtown club party (often hosted by and filled with Penn students), house party, or frat party--all in a single night.

Penn has a lot of school spirit, but does not have warm n fuzzy community love. It DOES have 10,000 people after all. Your community will not be handed to you like it would be at, say, Yale. Like so many things at Penn, you have to go out and do it yourself.

The comparatively dense campus means there are always students around, which definitely creates a feeling of energy wherever you go. Advertisement
Academics
Wharton and College at or near the top of their fields. Engineering, not so much.

There is a big emphasis on interdisciplinary studies. Students in all four undergraduate schools can enroll in classes in any other schools, and even some of the grad schools (like some courses at Penn Law). And of course the ability to add some business skills onto whatever you study is a great opportunity and one widely taken advantage of here.

Most professors are great at teaching, and definitely accessible, if you choose to access them (because they're not going go out of their way to access you). TAs are entirely hit-or-miss (if you get a miss, it's worth it to switch), and the workload is unbearable or a breeze, depending on whether you're trying to breeze through school or trying to maximize your education (i.e. are you going to take Classical Western Literature or Sociology of Pop Culture)

Student Body
With 10,000 undergrads (and another 10,000 grads on top of that) there is a niche for everyone. With so many places to find friends (dorm, class, groups, majors), I have large contingencies of preppy friends, artsy friends, fratty friends, brilliant friends, drunkard friends, city hopping friends...

Penn has an enormous international student population (1st in Ivy League by number, 2nd in percentage).

There is a strong party streak, but again, with 10,000 people it's not hard to find people who don't drink.

In Closing...
I would rather be at Penn than at Harvard, Yale, Princeton, or Stanford. There really is no place like Penn.

My only complaint is that campus housing sucks.