If I had just one observation about App Library, it's that you can only access it after swiping past your last home page, but the people who presumably would benefit from it the most are also the ones with multiple pages of apps that they downloaded but never got round to organising. So to get to it, they would have to swipe past the app they wanted to to access in the first place.
I wonder if it might make more sense to move App Library to the left of the home screen, replacing the existing widgets page. So it's always accessible one swipe away after you unlock your phone, which I imagine would be more convenient to reach.