Pros: hands on experience, opportunity to learn the ropes
Cons: comparably low pay, can be somewhat mundane
A 3rd party internship is a good way to get in the door and see how business groups operate day to day. Job tasks are not very complex, or ground breaking for an undergraduate. A lot of data entry, and admin. duties that otherwise take time away from full-time employees. Not at the level of an Intel sponsored internship, but well worth the experience.