Apple released iTunes 7.4 late last night.
At this time, the most important update to Smart Playlist users is the ability to rate albums and use this data in new smart playlists.
Please be aware: Ringtones added by 3rd party tools are deleted when you sync with iTunes 7.4.
And when right clicking a song, and selecting "show in playlist" or "add in playlist", the available playlists are shown with their header folders, if they exist.