Pros
Great way to learn how a brokerage firm works. As an Intern, I was on a rotation, working with the research and the corporate finance teams as well. They gave responsibility; the teams are very inclusive. Clients with holdings of big (e.g. Apple) names, makes the work very current!
Cons
Unprofessional work. Sometimes you feel you have to do much more administration, marketing, etc than you're supposed to.