I must enter 5 words for Cons but I really can't think of any. It's unpaid, but that is to be expected in this industry. This internship is an investment in yourself, as you will learn more than you possibly could in a classroom, and you will have an array of opportunities to meet artists and brush shoulders with pros.
Great thing to add to the resume because it is a well respected studio in the area. The equipment used in the studio is absolutely incredible and the studio itself is very nice! You have the potential to be in the studio at times when they are great musicians around, I was in the room during a practice session for a Grammy winner.
Cons
There is a lot of meaningless busy work for interns to do. The only work I consistently had to do each time I was there was dishes. I don't mind doing this kind of work but if all I am going to do each time I am at the studio is sit on my laptop, do dishes, and other meaningless busy work, then I could have stayed home for the day.