Petterbbb / elena - the Cybook has bookmarks and remembers where you left of reading the next time you start, so finding your way back is not an issue (unless the file system is corrupt).
Martin - The concept of horsepower was invented as a measurement that people could relate to. Last time I checked there were no horses inside my car, neither could I find traces of James Watt or James P. Joule in there. It is however convenient to have something else than a progress bar to refer to when driving (and when bragging to others).
The ebooks (actually more than pbooks since they are not physical) need some kind of measurement to inform the person reading of how long the text is and at what position the text currently displayed is related to the full text.
When operated carefully, most ebook readers (the machine) can show a screenfull of text, this could be referred to as a "page" or "rendered page" and used by the SW in the reader to communicate quantitative qualities of the ebook and the reading session. Of course other suggestions have been put forward in this thread and the other threads concerning this topic on this forum and also the wiki regarding
page numbers.
The progress bar is better than nothing for sure, but besides being buggy implemented, it lacks precision and flexibility and it does not give any information about the actual length of the text.