Pros
Protiviti offers a lot in terms of opportunity to perform at a level above yours. There are many opportunities to receive leadership opportunities that, I think, would not be available at a lot of other firms. This is probably due to the relatively smaller size of the company. Also I think the chance to be a part of a growing company with the ability to forge your own niche is there. Like most firms, Protiviti offers good (not great) benefits, bonus compensation, and a good amount of paid time off. Protiviti has a somewhat entrepenuerial spirit because of the aforementioned size and place in the market.
Cons
Management is out of touch with staff, in terms of what staff find valuable in work experience. Employees have little to no bearing over what experience they will receive and often have their wishes disregarded quickly after voicing them. Management within the company seems to lack the pedigree and experience of some other firms. While one would assume them to be the most motivated group in the company they often seem to be the least motivated (apart from a select few). Staff often both plan and execute work with little regard from management. This lack of care, oversight, and general will to work leads to finger pointing when things don't go as planned. Accountability is severely lacking outside of the staff level.