Extracting the lyrics takes a while, that's why this search rule is rather slow and that'y why SmartPlaylist puts the lyrics in a cache to make the search faster the next time (and that's why you have to use "Empty cache after sync" once you change the lyrics in iTunes).
You can also read the lyrics in the detail infos for a song, where you can copy some text as usual, or look up the meaning of a word:
- Store the lyrics inside your mp3s in iTunes or with other tools. (SmartPlaylist does not search for lyrics in the web)
- Get the lyrics to your iPod / iPhone / iPad by syncing to your device. Currently this does not work for songs downloaded from iTunes directly to your device (see other posts)