Certainly I think the new feature is accurate as a reflection of how long it will take to read the chapter you are currently reading. This is helpful if you are looking to find a stopping point in the next few minutes.
I think that the overall time for reading a book is good to give you an idea of the size of the book. For example I have two books of about the same length but the reading time for one is a good bit less than the other. And it makes sense since one is a fast read piece of fiction that is action driven and not a book that gives you pause to consider the brilliance of the language. The other book is denser with a larger vocabulary and more complicated sentence and paragraph structure.
One thing that is not clear to me is how this calculation handles the bibliography and index sections of non fiction books. Does it calculate that as part of the reading time? You might have a nonfiction book where the end notes and information is about 20% of the length - and clearly most people don't read all of this information.
As for page numbers, I just don't think that (for me) page numbers are applicable to e-books. I think that page numbers are old technology and just don't translate to the new world of electronic reading. I am not sure how great a job page numbers did in the old world either. I know that I track each book I read and often use Amazon or GoodReads to get the number of pages. It is amazing how much this varies by edition. I personally think that 'percentage read' and location numbers gives a much more accurate representation. My "Page Numbers" would be different from 'yours' because I am using a different font and a different font size. My 'page' also varies due to my margins and spacing between lines. With the exception of a new book where there is only 1 edition, I don't see having a page number comparison being useful in e-books.