Pros
Internship program is well-managed - a few fun off-sites and good community among co-workers. Work component was excellent. Interns are provided with both a leader/mentor who oversees the project and a sort of "buddy" who provides day-to-day help and camaraderie. Internship was an excellent learning experience, as my mentor put a lot of effort into giving me an achievable but challenging product with real impact - something I could be proud of. Also, free food.
Cons
Quantcast sports fairly decent facilities, but doesn't quite rival the absurdity (read: Odawalla smoothies - I'm looking at you, Google) of creature comforts that one might find at a big-name tech company. Overall, for a ~700-person company, I found the perks provided to be excellent.