The skill test itself is not very difficult at all, however their case interviews require knowing their format. I did not find the cases hard and in fact got hired at another consultancy but Mckinsey's feedback to me was to memorize their format and stick to it. It was less about the answers and more about knowing I had reviewed and studied their process intently, which admittedly I did not even look at except for the short webinar the weekend before. Practice and learn their process. Overall, a bit of arrogance from those I interviewed with leading me to question the culture though I cannot speak to it.

Rigorous but fair questions - mostly case based. Two sets of interviews x 2 rounds. You only get invited back for the afternoon if you pass the morning round. They expect a high degree of mental math and creativity. Worth prepping for standard case interview style questions, using frameworks but able to adapt them.