Mac Smart Folders

I've previously posted some tips on using smart folders on a mac, here's another one from MacWorld, Smart ways to work with smart folders. It contains at least one thing I didn't know...

"OS X lets you create a smart folder from within an application’s Open or Save dialog box, and then save it so that it’s visible only when you’re using that application. Start in the application, and choose File -> Open or File -> Save. Press Command-F or click in the Spotlight search field in the dialog box. As soon as you type something, the search bar appears just as it does in Finder search windows, letting you set parameters such as the scope of the search, and even add criteria bars. When you click the Save button in the Search bar, the dialog box that appears provides a special option: Display Smart Folder For This Application Only. Check the box, and a new category—Saved Searches—appears in the dialog box’s sidebar, with your new smart folder listed beneath it. Every application gets its own personal Saved Searches list, and none of these smart folders show in the Finder sidebar."

It sounds like that's only useful in an apps Open dialog, because you can't save to a smart folder.

Smart folders can be really useful, but in practice I don't use them very much. I don't use any in the Finder. I have a pretty good organizational scheme for my Documents folder and use Quicksilver (or spotlight) to find stuff quickly. I use a few in Mail, mostly to filter out messages to mailing lists without removing them from Inbox. I used to use a Recently Viewed mail folder, but now that I use IMAP with GMail and don't copy the enormous Archived folder to my mac, it's less useful since it doesn't show deleted (archived) messages.

Do you have clever uses for smart folders?