At most curiosity of listening to it once and then never again
Although there is an exception of Charles Mingus Tijuana Moods 2CD where I actually prefer the extended alternate takes over the studio version
I will also give a thumbs up to White album Kinfaun demoes due to acoustic versions of the album
I will say that if you were a Prince fan you probably should listen to the box set to Signs if the time. This is because it has some aborted ďDream FactoryĒ double album. Prince had truckload of unreleased songs. Which is fundamentally different of having new unreleased song rather than hearing demo, remixes and singles edit. However since I dislike Prince I canít say I like it but I can easily see hardcore Prince fan loving it.
However in terms of recommendations
Anything that is a complete discography collection ie Pink Floyd discovery box or The Beatles Stereo Box. You can get their discography in a single purchase which is good and convenient
Any deluxe edition that compiles b-side is worth a listen. So Radiohead 2CD/DVD reissue of all their albums up to Hail to the thief as well as the oknotok and kid amnesiac. As someone who collected their singles itís a bit of a duplicate but for newcomers it is essential and convenient. If you are game you can also try the 16 hours minidisc release of Ok computer which is worth it due to unreleased tracks early versions of songs appearing in later albums and live performance but it is not for the faint of heart
Also any box set or deluxe edition where there is a focus on live performances is worth a listen
Joy Division 2CD unknown pleasures has a tremendous live album with it that is just as good as the actual album.
I like the REM green box set due to the live concert
I am currently working through King Crimson and Gentle Giant mega box sets and their live performances are enjoyable. I currently quite dig the complete 1969 king crimson box set.
However itís going to take a very long time for me to complete listening to everything inside of it so I canít say I finished it yet for me