Pros
While not everyone outside of New York will know the name of the overall company, they'll definitely know one of the titles you work for (GQ, Vogue, The New Yorker, etc). Great for a resume. The things you work on (style, fashion, food, travel) are probably a lot more exciting than working in insurance or accounting. Once you're in, they are very good about letting you jump from publication to publication. So if you're a marketing associate in one group and the path to marketing manager at your job is blocked or one opens at another magazine, you can switch over and get a raise/title that way.
Cons
Entry level employees can be overworked and underpaid. If you're getting into the magazine publishing industry now, you'd be blind not to know that the industry is undergoing a drastic change.