From what I've read, though, most of the lag/slowness issues with eink are due to bottlenecks in the supporting electronics, which have relatively narrow channels to the display, and not a lot of processing power. Apparently the focus of most current eink tech is (understandably, given the established markets) power saving and cost, with update speed losing out.
I saw a video a few years ago, where someone had bypassed all that, and was running an eink display at video frame rates. It seemed to work fine.
There are other similar videos, by other companies, too.
So for a device where more power consumption is acceptable (compared to a power-sipping e-reader), fast-update eink displays may well be possible, and even practical... but it's not so clear anybody is putting much investment in such a thing...
I have waited impatiently since the 1990s for a functioning E-ink reader with fast enough page turns to browse documentation.
And the reason it isn't here is not technical problems -- it is because some shaved chimpanzee of an MBA thought high quality E-readers without colour (or a battery good "just" for a few days) was too small a market?!
I reviewed snogglethorpe's link and then searched a bit. Apparently the same company that made that demo also makes an ebook reader. I don't know if it is cool or not. I don't know their stance on Free Software and Open Hardware. But... They do have a 'video' tag on their blog. http://blog.bookeen.com/tag/video/ Cheers!
