Pros
They give you a lot of training and responsibility so it is a great place to grow into a professional. They are big on development and take an interest in your personal life (which for some can be a "con"). Lots of "happy hours" and team building. Very fun atmosphere. Since it is staffing, you learn a lot about other professions and it makes you a more well rounded person.
Cons
The pay is terrible. The commission is almost no existent unless you are lucky enough to be given an account manager with a good territory and high volume accounts. There is no work life balance. You will NEVER work a 40 hour week, it will always be closer to 50 - 55 hours a week. Lots of work with very little pay out. Great for getting your foot in the door right out of college though.