Pros
Opportunity for exposure to wide range of companies, industries, and people. It's a great name to have on your resume if you don't stay long, and there are opportunities to keep moving up if you like what you're doing. In general, you get to work with competent people. This is a good place to work if you have initiative and are willing to express your interest in particular career paths. If you aren't assertive, you will be stuck with the worst jobs working with the worst people. I recommend building rapport with a number of people you like working with and try to stick with them on all projects.
Cons
With the recent hiring spree, quality of employees has declined. The recruiters will downplay this by saying quality isn't decreasing even though they're hiring tons of people, but that clearly can't be true. There are new people I worked with that made me wonder if a pulse and a college degree are the only requirements. This is why I recommend finding a core group of competent people to work with, which is possible if you're assertive and demonstrate your own competence. If you're not assertive, you'll get lost in a large team and no one will take care of you. Also, the pay difference between high-performing and low-performing employees, at least at the lower levels, is quite small.