I listened to a trilogy once and then saw the paper books and regretted not opting for the paper book option, even though I don't usually have patience for paper: each book in the trilogy was written in a different color font and totally matched the cover and overall mood of the novels.
Blue (can't find a pic) -
Red -
Green
Makes me wonder what else I am missing out on, and how cool it would be if color eink was commonplace and used to its potential by publishers....