Pros
I wanted to reply to the intern who posted that this isn't a good place to intern at. I disagree. It's really what you make of it. If you work hard and prove yourself they'll give you awesome projects to work on and treat you like the employee you are. If you slack, they won't. Simple as that and same as any other internship. That said, the program they have there is wonderful, and one of the best experiences I've ever had. And if you take an internship that isn't something you're interested in or that has nothing to do with the skill set you have to offer just because it's Conde Nast, that's your fault for settling, and yes, you will be miserable.
Cons
Biggest (and really, only) con by far is trying to live in New York on a lunch stipend. Unless you have rich parents (can't say I do), get saving up, because even living frugally you'll blow through a few thousand dollars doing this.