Do you have an example PDF for that? For the average use, TeX is overkill (sometimes OK), but if you need the finest possible typography, TeX yields its power. And then the XSL-FO formatters are pretty fast disappointing.
AFAIK, the vast majority of O'Reilly books pass through docbook at some point (many authors write in docbook directly, some portion of them use asciidoc like us), so if you look at any O'Reilly PDF ebook, chances are good it was generated from docbook (at least as an intermediate format).