I will pretty much echo what Steve and DonM said, in that I use the Songbook extensively, especially to create 'dedicated' playlists, i.e. Christmas, St. Valentine's Day, Italian, Irish, Patriotic, etc. ... I also make use of the 'Favorites' and User' sections to store Styles I have edited: changed drum kits, bass and other 'arranger' voices, set STS, etc., to fit certain songs, and have renamed the styles using the song titles for quick access ...
I have also renamed many of the 'Favorite' banks to indicate what styles are there, i.e. Christmas, Italian, Irish, Patriotic, Ballads, Swing, Latin, etc. ... of course after I upgraded to the latest OS, I had to rename those Favorite banks, but that's another story ...
However, I have not made much use of the 'Performance' section, other than to use a particular factory voice ...