In iTunes, I want to sort my playlists by most-recently-accessed or most popular, rather than alphabetically.
Cosign. - Stephen Mack
I have playlists based on play count, which is my stand-in for "popularity". But the play count metric doesn't get bumped until the song ENDS, so I often tell my wife not to skip to the next song early because I want to "get credit" for listening to it. - Brian Johns