Enable browsing in the Dash
I see no reason why the Dash can't allow hierarchical navigation in addition to searching and filtering. It's not like displaying categories that the user can navigate into is going to interfere with the other functions. All you need to do is display in the "results" section a list of categories followed by results that don't fit in the categories. You can also elect to only display categories when not using the search, so they wouldn't crowd out the search results when users choose to search rather than browse. This would then allow lenses to organize their content in hierarchical fashion, so the apps lens can display a list of app categories instead of a disorganized mess which is the situation today. I sure hope you get this done before 12.04, because without this feature the Dash will simply look bad and be annoying to use, especially for people who don't like to type in search terms for each and every thing they may want to open.
There are other uses, such as navigating directories in the files and folders lens, organizing music into albums in the music lens, sorting mail into folders or conversations in a mail lens, and more.