I just inadvertently changed all 65 of my paint colors to grey! It's great that attributes are now in folders, but this was a whole folder full! Since there is no undo for changing attributes, I had to go back and reload them from a previously saved version of the file. That worked, but an "Undo" would be much simpler.
Another good reason for an Undo: I don't always know if changing an attribute is going to give me the effect i want, so I may make an experimental change. But there is no undo to go back to the way things were if the change doesn't work, so I must carefully document the way things were before I make the change.