The roles are quite difficult to get, so congratulations first off. For the August 2011 intake there were something like 70+ applicants per place, so quite heavy competition.
PI is the flagship of the advisory arm (ITRA, Risk, and FS lag behind a bit) and is doing quite well. I have gone through the graduate programme and there are some great things and some things that are lacking, as any other, but I could not ask for a better group in terms of classmates (Main universities represented at Oxford, Cambridge, LSE, and Warwick). Are group gets on extremely well and with only a few exceptions all work hard and play hard as cliche as it sounds.
In terms of our competitors I'd say ahead of KPMG, on par with PwC (but we pay better), and a behind Deloitte as they never got rid of their consulting arm as the other Big Four firms did.