The cleanup involved in the 1993 release actually did remove a lot of dirt and scratches. The immense amount of dirt in the pre-THX LDs is evidence enough. But the cleanup didn't remove everything and the ghosting it left behind is almost unbearable for me to watch anymore. You'd be surprised how many burn marks were still in the video after their extensive cleanup job. All of these will be absent from the X0 release, as will the shots horribly affected by the DVNR.
I've said many times in the past that I have no doubt the X0 will be better than the OUT, and I still stand by my words. Though if the OUTs prove to be much higher quality than any of us anticipate, I will graciously bow to Lucasfilm's effort and take a large helping of crow.