I proofed and inputted changes to five more chapters, and then proofed the rest of the layout. I'll input tomorrow--inputting changes is really tedious. Still, I can see that I got more adept at layout as the book went along, because there are far fewer art issues in the later chapters than in the earlier ones (and I don't think that's just fatigue speaking).
But I did find a continuity error in the last chapter! Oopsie! Well, that will be corrected soon enough. It is, however, an argument in favor of not putting up the e-books until after I finish laying out the print-on-demand version--you do just reach a point where you're so familiar with the material that you glide right over mistakes, but after it's laid out I think it looks different enough that it give you fresh eyes.
Of course, it's never going to be perfect. At my first job in publishing, manuscripts were proofread three times after editing, with a grand total of four people involved in each proofing. Then the layouts were proofread twice, and then after the book went to the printer, we got another set of proofs from them, which were read over. And there were STILL errors in the finished books!