I was a software development summer intern at the Mass lab in Littleton, MA. The location is really nice during the summer, and the premises feel pretty new. This probably varies for each intern, but the team I was in was really nice and willing to help me with my problems, and we all got along pretty well. Pay depends on the number of credits towards your degree that you've finished, but the rate is relatively good.
Cons
Even as an intern, you can feel the bureaucracy going on in the background. Also, this depends on the team, but be prepared to have a lot of meetings, most if not all of them including having to deal with the joy that is conference calls.