Vantaggi
I strongly recommend the internship experience at Language International. You'll get a ton of real responsibility -- no fluff or marginal work.
As an intern, I got to learn an amazing amount in a short period of time. The management team will entrust you with as much responsibility as they think you can handle, so you don't get stuck in a position that doesn't allow you to contribute to your full potential. They really help you learn and improve quickly.
The fact that there were a bunch of other cool interns was a plus, and the fact that the rest of the team was pretty cool made it nice socially.
Of course, it's also just cool to work for a start-up, especially one that seems to have so much potential.
Svantaggi
It's not the right place for everybody. A project management internship at a start-up requires dedication; there's often a need to stay longer than most of the other interns to get things done. With that said, most internships seemed more laid-back than mine. Also, some internships are unpaid (as you'd expect with start-ups) but it's a fair deal: you get lots of value out of the experience, so as long as you're living with your parents still, it works.