We found that although customers could review changes before save, most did not and would save changes without checking and then when there was a problem would not be happy, this was especially an issue with new users of Jaikoz.
So with SongKong we took a different approach saves are made automatically, but if customer finds an issue at a later date they can use Undo Changes to undo all changes made by SongKong to any folder (and sub folders). This is because all changes are stored in the database.
Also SongKong processes folders independently and saves as it goes along, this means it doesn't have the same memory requirements as Jaikoz, but also means there would not be an obvious time to show the customer possible changes because save for one folder are happening in parallel with changes in another folder.
Having said that sometimes customers just use SongKong to fix a specific album. When working one album at time I can see the advantage of optionally allowing the chance to review changes before save and we already have plans to add this.