Just noticed three small problems:
1. Sometimes using search isn't successful for whatever reason, so obviously the user will utilise another method to find the lyrics. However, once the lyrics have been found, it is impossible to manually paste them into the edit window because an alert pops up telling you there aren't lyrics for the song and asking you to search first. Of course, it is possible to paste the lyrics directly into iTunes but I it would be more convenient if the application were to allow this type of pasting.
2. If you close the main window in error by clicking the red close button you can't reopen it unless you relaunch the application. The main window and the search window should both be listed under "Window" in the menu bar permenantly and when one or both of them is open a tick should appear in front of its name.
3. If you zoom the search window you cannot make it smaller again by clicking zoom, unlike the main window.
... but it's still the best application of its kind!