Not surprising, but very useful. If you Option-Click on the "i" symbol next to an item in the Spotlight search results window, all of the items in in that section only will show the "expanded info" view. Option-click again to collapse them all.
This is consistent with the usual behaviour of the Option key, but I can't find any documantation, so I thought I'd post.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20050509065359954