Pros
As long as you're not completely useless, it shouldn't be hard to get a "job" here and get some experience you can apply elsewhere.
Cons
Principal staffs exclusively barely-paid interns ($100/month for a full-time position!) to do work that should really be handled by full-fledged designers, which is both unethical and actually illegal. Beyond this, interns are regularly kept beyond their scheduled hours--leaving the office on time is the exception, not the rule. Worst of all, the work environment can be very toxic; principal is demanding, temperamental, and rude most of the time.