Depends what you mean by casually, I did my research for both my interviews and i think I was pretty thorough. However, I certainly wouldn't want to appear too uptight in the interview and I definitely enjoyed the conversational approach at KPMG - contrasted with the more formal feel at PwC.sdfjsdkl55 said:Taking an interview casually will definately score you no points.
Taking it in a 'casual' sense isn't necessarily bad, but as others have said research is important. I suppose there are always exceptions, one friend who got an EY offer apparently did no research and his answers were pretty blunt and direct - or for lack of a better word stupid (at least in my eyes).
In the end, I think to a large degree it always depends on how lucky you are in terms of the partner.