Pros
The Workman family still owns and operates the company, and they are wonderful people who care deeply about books and their employees; it really is like a family there. The books are unusual and innovative, and you'll work with lots of creative people, authors and staff alike. You'll also get to try on many different hats; everyone's unique talents are valued, and you're not allowed to say "That's not my job." Senior staff members make excellent mentors.
Cons
Lack of "official" job titles (and maybe other things in the work environment, though I'm not sure what) makes upward mobility difficult. At least in low-level positions, pay is low (pretty standard for the industry, I think), and New York City is really expensive. It can be fun to take on lots of new projects, but it's common to find yourself working (really hard) on things that you'd never imagine would fit into your "job description."