NEW: Refresh Smart Playlists v1.0
For years my go-to Smart Playlist has been one called "100 Songs Or So", which is essentially a bunch of tracks that haven't been played in a few months (plus no Holiday tracks, songs shorter than ten minutes, and so on). Early on I figured out that the contents of "100 Songs Or So" could be refreshed by deleting all its tracks and allowing it to dynamically re-populate.
It was suggested to me recently that it might be advantageous to perform this kind of refresh on more than one SP at a timesay, just before you sync them to a device. Sometimes I wonder why I don't think of these things.
Refresh Smart Playlists will display a panel from which you can select the Smart Playlists in iTunes that you want to re-populate. Click the refresh button and they're instantly updated.
The Smart Playlists you've selected will be remembered the next time you launch the script so you can quickly refresh your favored SPs without having to select them each launch.
Not every Smart Playlist is "refreshable", of course. For example, if a Smart Playlist already contains every track from the library that meets its criteria, its tracks can't be deleted. A Smart Playlist that uses "Limit to" and "Live updating" criteria is more inclined to be dynamic.
More information and download is here.