I wanted to be able to toggle from big to small window using the keyboard, so I assigned a keystroke (Command-Option-M in this case) to the Zoom menu item (through Panther's Keyboard & Mouse preference pane). However, when I went to try it out, to my surprise iTunes actually zoomed the window like normal apps. It took me a while to realize it was due to the Option key that was part of the shortcut. I reassigned the shortcut to Command-Shift-M, and now the window toggles correctly. However, Command-Option-Shift-M does not zoom the window, which is annoying.
So when you're assigning keyboard shortcuts to applications, watch out for behavior that changes with modifier keys.

