I was trying to figure out the name of a few files in an album I have. As I figured out the name of each song, I went through and renamed the file (the actual file name, mind you). Imagine my (pleasant) surprise as Amarok briefly grayed out the playlist entry (as the song was missing) and then immediately ungrayed it as it identified the song under the new filename. And then kept going through the playlist without skipping a beat.

I have nothing to say beyond that. It was just neat.