Pros
The people really are fantastic. Because you're put in a position in which you'll be interacting with potential advisors on a daily basis, they only hire people they know have solid interpersonal skills. As a result, it's a really social space. Coupled with the fact that they're increasingly only interviewing high-caliber academic individuals leads to an impressively social and smart work environment. It's also exciting that they are fighting to keep the startup vibe alive. From the get go the MD said to all of us that if we weren't finding a way to try and make the company itself more efficient and valuable we weren't doing our job.
Cons
At the end of the day, your primary role can be closely likened to working in a call center if you let it. Unless you work hard to really get a grasp on your project (the background, the players, etc) and actively try to learn as much from it as possible, it can quickly become repetitive. Because it's so young and has had incredibly high retention, there's some uncertainty about next steps for analysts that don't want to continue moving up the ladder. Finally, pay is not where it needs to be at all to be competitive with other internship offers.