I'm going through my new book, The Songs of Chaos, for the final content/structural/does-it-sound-like-crap check. It has been line edited twice, spell checked by two people and computer, and beta read twice.
I'm now to the point where I am tweaking things, and then going back later to restore the text to its original form. When you start second guessing your own second guessing, madness is not far behind. I even have a cover that I am instructed in no uncertain terms, "Leave it alone."
I always hate this part. It's scary.