The latest version of iTunes has an improvement that has made me tremendously happy.
Until iTunes 9.2, if you had a smart playlist parameter that said the song had to be unrated (un-starred), and — while listening to the playlist — you rated a song, the playlist would stop immediately because the just-rated song would disappear from it.
In the new version if you rate a playing song that disappears from a smart playlist, iTunes simply jumps to the next song and begins playing. Very awesome.
David Vincent Gagne