Sorry, I should have said, "they," not, "he." The classic edition and higher maths should be supplemented for students needing theory.
I did say that Basis is doing well with it, but they do have math majors teaching math. DS comes home with worksheets where saxon is lacking (eg, functions and determinants in alg 2). This is precisely how I feel saxon should be used. I just can't help being concerned, because I am not in control of who will be teaching precal next year, and precal theory is critical for a proper derivation of the calculus.
I am also sure that some homeschoolers are doing fine. The material is not wrong, unlike some "approved" high school texts. Certainly some concepts are being overlooked by these kids and/or their parents. I just have only come across a handful that did not require some remediation, and dozens who did. Their calculation skills were always strong, and their theory was always weak. It tells me that saxon is excellent at application. The bite-size approach seems to work well for that, while limiting opportunities for deeper development.
I found a review which matches my thoughts very closely:
http://cathyduffyreviews.com/math/calculus-saxon.htm. Mostly positive, with a couple of big caveats.