Pros
There is great flexibility at PwC - as you progress you have the freedom (as an assurance assoicate at least) to pretty much work your own hours, depending on the engagement. You could work from home now and again, or show up to work early and leave early, or show up late and leave late. No one really cares as long as you get your work done. Additionally, the people you work with are very good in general - they are pleasant and well mannered, and well educated.
Cons
The flexibility described above can be a double edged sword - there are times when it's taken for granted that you will take your laptop home with you and continue to work from home, or at the weekends, in order to meet some ridiculous deadlines on an understaffed job. The work/life balance seems to elude many managers and senior managers at PwC who assume that you will work all the hours god sends. And, like I'm sure most big 4 employees feel, the salary is poor for the amount of work you do. Many leave once they've got "the experience" and go on to do less challenging and higher paid work in industry.