Pros
One of the things I loved about working at Protiviti is that it has many offices throughout the world which presents a lot of travel opportunities. Unlike the big-4, there is no busy season. I really enjoyed their training programs. They encourage all employees obtain a certification (CIA, CPA, CSA, PMP, ect) and give you time to study for them (unless you are staffed on a large project). Pay and promotion structure is comparable to big-4.
Cons
My work schedule was very inconsistent. Part of the year I was very busy, while at other times of the year, I would spend months in the office because there were no projects on the schedule. This can be good if you are studying for a certification, however, this hurts your chargeability for the year and makes it near impossible to get your bonus. Time and expense reports are a pain, but a necessary evil in all consulting jobs. Pays less than working as internal auditor for a company.