I recommend using the HBS Guru without hesitation! 

(2+2) I can’t imagine going into my HBS interview without Sandy’s preparation.  After a busy fall interviewing for jobs, I was confident that I knew exactly what I was doing when it came to HBS.  As it turned out, however, the interviewers were looking for something very different.  Were it not for my call with Sandy, I don’t think I would have done nearly as well.  In his direct and helpful manner, Sandy told me exactly what I was doing right and what I needed to fix.  I felt absolutely ready going into my interview, and I came out knowing that I nailed it.  Using Sandy was one of the best decisions I’ve ever made–and I got in!