Pros
Gets you a foot in the door to large companies/firms and gain some practical experience.
Cons
Lowest possible pay; short-term positions that make for inconsistent employment and make you look unstable on paper; favoritism shown between who stays on for assignments and who doesn't; they have no vested interest in your development or even employment; any given Friday could be the day that you are walking out to your car at 5:00 and get a call saying that your "project has ended" and you are no longer needed. And they won't explain a damned thing to you as for why or have any new assignments ready for you to start. And it's at that moment that you realize that they have zero loyalty or consideration for you. You are not their client. The employer is. You are just a means to an end. A body that can be replaced with the next graduating class.