Availability is also one of the principal problems with e-Ink, and is directly related to the patent issue. It is next to impossible to source e-Ink displays (even at outrageous prices), or to work with E Ink corporation in any capacity unless you are huge and are in a market they are interested in. Making another generic ebook and can credibly claim that you might sell half a million? Maybe they'll talk to you. Work for Lenovo and want to put an e-Ink layer in a trackpad? "We're not pursuing that market segment at this time." It's not an open market, and they haven't been interested in moving beyond ebook readers for the last decade.
Smaller designers who want access to the technology can't get it from a western company, because none are stupid enough to attempt to design a competitor while E Ink the company is still around to sue them.
Fairly recently we've started to see Chinese electrophoretic displays crop up, and I can actually get a devkit or buy them by the low thousand, because E Ink isn't going to be able to sue them in China. But you still don't see them designed into very many products sold in the west, because it would be easy for E Ink to stop the end product from being sold.