I am now on my 2nd Paperwhite (gave the first to my wife) and I love it, except for one thing: I started with a Kindle Keyboard (then went to Touch, then Paperwhite) and I absolutely miss the progress bar that has the little markings showing how long each chapter is, and where you were in between. This was easily the most helpful feature of Kindle software. I find most of the other features (x-ray, annotations, notes, highlights, etc) useless. But that progress bar was the best thing about the Kindle.
I know that recent Kindles have the "time left in chapter/book" option, but it's very unhelpful. Its calculations are almost always incorrect. I will often set my book down to do something else (deal with the kids, answer a text message, etc), and when I come back to it, the "time left" feature has incorrectly interpreted such events as me taking longer to read a given page. So it will often tell me I have 10 minutes left in a chapter that in actuality I breeze through in 3 minutes. The visual progress bar, on the other hand, didn't try to predict such things. It just showed me where I was.
At the very least, give me the option of turning it on/off. Many users may not want it, but it is the one "can't live without" feature from the Keyboard and I am absolutely devastated and frustrated that it was taken away. Please, PLEASE bring it back Amazon!