@Saturday: I thought it started learning from scratch with every new book. Hmm, I'll watch it when I next start a book.
I love the time left in chapter as well, but to know I had 3 hours left in a great book, influenced me in that I made sure I had 3 full hours uninterrupted to finish it. That's when I first realized how very awesome the feature is. Before, I never even would have thought about carving out a specific amount of time.