The search facility on the extend/plugins and the extend/themes repositories are anything but reliable. The search scope should be limited to plugin/theme title and description (don't know what it is now). Search for one thing, find everything else but that! :-(
Also, there must be someway we could narrow the search based on criteria?
Btw, why are plguins and themes organized based on tags and not categories?! IMO, categories are better. You can let the plugin author choose the most-fit category for his plugin. What say?