As many kindles as I have had since, I still mourn the progress bar. It was just the best and most comfortable visual guide of a book for me. With little dots for chapters. It was just perfect. I still miss it terribly.
I still have the keyboard and the black button basic. But I need the light now to read. Once in a while I sit outside in bright light and read on one of the older ones and seeing the progress bar is a delight then.
I have send them feedback to their kindle feedback a few times about it. I don't expect to ever see it again.