Pros
Learning opportunities are unmatched anywhere. You will go to a lot of trainings (some may say too many, but I think the more you learn the more marketable you'll be elsewhere). You could come in as a new intern or associate and know nothing in the beginning and leave with knowledge that puts you head-and-shoulders above any other candidate for your next job. This may sound snotty, but I do not like working with a group of people where you are always the smartest person in the room. This is not the case with PwC. Your peers are the best of their respective specialties and you are too. It is very nice getting to work with such smart people. You'll rack up a lot of airline miles depending on which department you join (Audit gets a lot, Tax gets a lot too, but not as much) Also may sound snotty, but the name goes very far!
Cons
Early in your career, you will quickly realize that "PwC" on your resume will get you better compensated if you jump ship before getting promoted to Director. If you stick it out though, you are much more likely to be better compensated over the life of your career (stick it out is my advice). Another downside is that everyone you work with is so busy with their own work, some important things get put off until the last minute (e.g. your periodic formal reviews "PFF's as we call them", annual reviews). A couple other downsides include tracking your time on a 1/10th of an hour basis. Lots of people cannot get used to this aspect, but it is necessary to bill the clients the appropriate amounts. The "chargeable hours" goals can be difficult to meet as they are set very high and your success is measured weightily on this specific metric. These downsides are managable, tolerable (at least for me), and can be overcome by the right candidates.