Well you've got-
Remixed IaW tracks - they're an interesting curiosity, but the originals are better imo, so they're not worth it alone, unless you happen to really hate the production on Images and Words.
Through Her Eyes alternate mix - again, more of a curiosity that imo isn't as good as what's on the album, and if you want this, you'd be better off finding a copy of The Making of Scenes From a Memory that it's taken from, with the complete alternate mix of the album.
To Live Forever - If you like the song and don't have it elsewhere, here's a good studio version.
The Root of All Evil and Sacrificed Sons have shorter intros. I wouldn't really consider that a selling feature.
And various single edits, that are just less effective versions of what's on the studio albums.
Personally, I'd only consider this for new fans (and even then I think there are better ways to introduce people to the band), or completionists who have to have everything.