I have only watched SUPERMAN RETURNS twice: one in the theater, one when it was released on dvd. I own it in a SUPERMAN Blu-ray boxset, but I don't ever watch. I say this just so you know I can't remember every single bit about the movie, other than I wasn't a big fan at all. It bored me, had no emotion, and I thought some of the cast was lame.
Given that, I thought this edit was great! It couldn't help some of the problems in the original, but did make the pacing better and seemed to make the story work a slight bit better because of that.
The editing was superb. I think I noticed one spot where I could tell it was changed for this fanedit, but that was it. Audio and visuals were great.
Even though I don't care for the original, you made a great effort with this. Despite my feelings on the original, your score for this shouldn't have to suffer. 10's all around!