Jeremy Frumkin has a nice short article in OCLC Systems and Services:
However, in order to do all of the above, behind the scenes my digital library without golden bars uses all of the expertise and experience of libraries to create a successful user experience. Instead of showing MARC records to users, it uses MARC records to improve search relevancy. Instead of making a user click on a â€œget this itemâ€ link, and then popping up a separate window with information from an OpenURL resolver, it smartly steps ahead and provides a direct link to full text in the search results themselves, based on the information provided by the OpenURL resolver. In other words, it performs extra steps so the user does not need to.
Worth the quick read.
Update: Jaf has posted the text of the article on his blog.