I have been using some PostScript-specific macro packages in the books I have written. Also, when I tried to use pdfLaTeX to typeset a book with several hundred pages, pdfLaTeX ran out of space for the PDF bookmarks etc.

I later corrected this problem by modifying the local TeX installation. I configured the TeX system with more space for bookkeeping (I don't remember all the details any more). So, you may have to have a non-standard version of TeX to use pdfLaTeX with longer books.

Update: A message from SP clarifies the situation with pdfLaTeX: "[The problems are] probably mostly memory related. Like back in the early 1990s, when we had a separate 'BigTeX' binary and formats. I thought they had increased the default memory settings to reasonable values when creating more recent versions. But probably they didn't quite foresee all the nice PDF stuff people were going to want to use. Let's hope these memory considerations in TeX will be history in whatever TeX is being developed to (NTS, say)."