I'm not sure if this is new in iTunes 7, but given the layout of the library pane, I suspect it is. I discovered this entirely by accident, and I'm not sure if it's actually useful in any way, but I submit it for everyone's enjoyment nonetheless.
It's possible (and very easy) to convert a smart playlist to a regular playlist: just drag the playlist from its current position in the Library pane up until it's over the PLAYLISTS label. Drop the playlist there, and a new regular playlist will be created with the current contents of the dragged smart playlist, only without the auto-updating features. The smart playlist will remain as it was, so you don't lose anything in the process.
Mac OS X Hints
http://hints.macworld.com/article.php?story=2006091802333642