Pros
Very structured internship, provided just enough guidance to transition you from thinking like a student to thinking like a professional without being overbearing.
Remarkably flexible for emergencies and time off. Complete 180 from the typical job a high schooler might be familiar with.
Meaningful work. Able to acclimate with testing and familiarizing with the code, then eventually progressed to creating a full feature solely developed by interns.
Cons
The summer is maximum 4 months long, can't stay any longer without working through school.