Hi
I went for an assessment day last week at pwc and now I have an internship!
The group exercise was fine. There were 5 of us, given 20 minutes to read through some material and write some notes. Then we discussed it for half an hour. You need to make sure you get your points in and speak clearly. Always think what you're going to say and make sure it's relevant to what other people have said or the point that you think needs making.
My interview was good, the guy was really nice and made me feel at ease. Basically he asked me about different business situations, but don't worry, none of it was overly complicated! As long as you have a rough idea about business, and know about the issues surrounding their business you'll be ok. They seem to like asking you about the general issues surrounding professional services work. I'd advise knowing about the enron and worldcom stuff, as they seem to like asking about that in interviews!
Otherwise, good luck, relax and be friendly and you'llbe fine!
Which office and service line are you going for btw?