OK, maybe it's because I've never actually been impressed by the various CMS search mechanisms before. TikiWiki was slow, CPGNuke is slow and often times out on me. Neither of them had a built-in mechanism for searching custom content. But Drupal handles searching the custom fields I've added to the book module just fine, and does so reasonably quickly.
Granted, it's only in test mode with a hundred items so far, but I'm still quite pleased that I've got full text indexing going on.