I *would* like to try the book-cover screensaver, since I never get to see the book cover, the way I currently use my kindle! I still have ads; I only view the "text titles" version of the home index; and opening a book starts *after* the cover. I never see the covers, unless I actually look for them.
Still, I haven't yet wanted it enough to pay to remove the ads, little though that cost is. Plus -- without the ad, doesn't my magnetic cover opening take me straight into the book anyway (no pause to swipe), and I still don't get to see the cover-as-screensaver? So it hasn't seemed worth it.