The people that work there are amazing, as are the other interns. Some of my best friends have come out of the summer internship at MATTE.
What I wish was different
The fact that it was unpaid is unfortunate, although they do offer a $15 lunch stipend for interns.
Advice
The people and the network that you build working for MATTE are unbelievable. Additionally, the clients are really cool and you get to attend tons of parties in the city.