Hi, wun_8_seven. I did the Advanced course at Chapman Academy in 2001, and had a ball! The Bianchi Cup had just finished, and we got to use all of their stages, steel, etc. There were only 6 of us on the course, so we had a great deal of individual attention from John Skaggs. That, plus the fact that all of us had had quite a bit of prior training (a prerequisite for the Advanced course), and therefore came in at a pretty high level to begin with, meant that we learned a whole lot during our week together.
I can't comment on the introductory course, but based on the superb quality of the Advanced course, I must assume that it's at least as good in its way, and I can certainly give John Skaggs a top-flight recommendation. (I understand from Massad Ayoob that Ray Chapman hand-picked John to run his school when he retired: and I know from personal experience that it was an inspired choice!)
Mas also calls the Advanced course "the Harvard MBA of handgun shooting courses", and in terms of the amount of stuff covered and different skills learned, I'd have to say he's not far off. Personally, I'd rate the Level 3 courses at Thunder Ranch and/or Gunsite (the latter known only by reputation, I'm afraid) as being at least as good. However, the fact that so many very professional organizations train at Chapman Academy is a testimony in itself to that school. (The Navy SEALs had been there a week or so before our advanced class, and John was still muttering profanely to himself about their marksmanship with MP-5's on full-auto... they had shot both wing mirrors off the school's Toyota Land Cruiser during the shoot-while-driving scenarios!)