Difficult as in how? Its all relative.
Their average GMAT is around 620 and GPA is 3.3 if I remember correctly from the info session. (all this info is easily accessed through BusinessWeek link below)
Their yield is higher than most, but I think there is a lot of self-selection as well as the AdComs working with the applicants. They will also sit down with you and go over your chances and improvements that can be made. I went in and talked to an AdCom and it was a semi-interview and they started a ghost file on me. I'm glad it went well as I was not prepared for that, but now you can be.