I used MKSAP 2 to study for the IM shelf (Feb 2006) and found it to be an excellent preparation for the exam. Unlike the majority of other resources that I utilized or skimmed through, it had a question format very much like the real thing. Although I felt the difficulty of questions was overall a notch above the shelf, I was surprised by the number of questions on the exam that I only got right because I had encountered them before on MKSAP. I don't know how much MKSAP 2 differs from 3...but likely either would be a good option to use to prepare for the exam.
Good luck!