Yeah, HSHHC is a *very* badly written book. Weissbluth really should have found a better editor. Or have someone else write it for him!
That said, both my babies have been textbook HSHHC. We didn't have to let DS CIO at all, he just fell into the patterns more or less perfectly. DD, on the other hand, needed some tough love to get over a couple night wakings, but for the most part follows his patterns pretty well as well. I think we just have a harder time with her because we can't keep her schedule as well when there are two kids to care for.
I do find it annoying that he doesn't have better solutions for families with more than one kid. His solution is to get or hire some help to watch after the kid at home. Well, I'm not going to pay a babysitter $15/hr just to sit at home and watch my baby sleep everyday! He needs to give more practical solutions for this very common situation.