One idea we've kicked around is to make the eventual "components area" on zope.org such that component users can provide some +1 -1 type feedback that is incorporated into the way that components are listed on the site. This would let the most popular / best components appear at the top of listings etc.
Have you had a look at http://www.php.net ? They have a "PHP Annotated Manual" (right under Documentation) where users can add comments to the pages. I always found this very helpful, but it may be too much work for DC to read over every comment (php's annotations are moderated). Perhaps just allowing members of zope.org for the comments and/or letting the maintainer of the product moderate it might solve that. This might be a nice suggestion to the rating system and could all be made configurable by the product maintainer. cheers, oliver