Electronic Ink Uses No Power While the Screen Is Static: Great news for when you go on a long vacation in a place without electricity. Or if you read really slowly. I do neither very often. Of course, it's impossible to say bad things about long battery life. But the kind of reading I do is generally around the house, and my house has power plugs. And I only need a few hours of battery life in such a device to get my daily reading quota in, so this argument doesn't hold water for me when on a plane or at the park.
E-ink Causes Little Eye Strain: Because e-ink is not constantly refreshing like a traditional gadget screen, it doesn't wear your eyes out. That's the theory, but yeah, I don't really complain about reading on LCDs either. And I do that for 12 hours a day. In fact, when LCD monitors came out, the argument for them was that they strained the eye less than CRTs. The youngest generations are already growing up staring at devices with glowing screens—are they all going to go blind as a result? I'm not going to lie, I think that reading e-ink is soothing, but it's not the most important thing in display tech, especially when I already know I can stare at a computer all day without issues.
Black-and-White vs Color: The majority of books don't need to be in color, but there plenty of reasons why you would want it: children's books, photography books and cookbooks, to name a few. Well, you can have it! There's talk about color e-ink, but what we've seen so far isn't very pretty, and those screens will still be unable to refresh in a way that would support video. Amazon's boss, Jeff Bezos says that a color Kindle is "multiple years away," though Plastic Logic's Barnes & Noble reader may be full color.
The real alternative is LCD. It's already in color (in case you never noticed) but it has to improve its power management. The key to this is becoming more transflective: Some screens are designed to be seen with ambient light (like e-ink), and operate with relatively low power, but when needed, they can get a boost from a nice even backlight. There are plenty of transreflective techs—including panels from Mary Lou Jepsen's PixelQi, which started out as the screen first seen on OLPC's XO—that'll be available in the coming years.
E-ink Refreshes About As Fast As You Can Turn a Page Good enough for books, but the future of media is—kill me for saying this—multimedia. Moving, alive, living and interactive. We're talking about moving video and charts, as well as hyperlinks. All the live action of the web with the strengths of print. E-ink is superior for replicating paper, but it can't even support realtime cursor movements or button presses, let alone video. Besides, what's the relative amount of time you spend reading books versus your other media consumption? I bet, as a gadget geek, you spend a lot more time reading web pages and other modern forms of media. Which brings me to...
E-Ink is the Best Tech For Digital Dead Tree Replication: There's no doubt at all that e-ink is a great tech for replicating black-and-white dead tree content read at a snail's pace, while you're miles away from power. But even if they solve the color problem, there are a few more nasty items on the to-do list. Sony has all but proven that any kind of backlighting and finger touch interface destroys the benefits of e-ink. The touchscreen Sony models are not easy on the eyes, because of their tremendous glare. The so-called touchscreen readers from IRex are actually powered by Wacom pen technology—you can't turn a page with your finger.
Crippled as these more "advanced" readers are, they still don't come close to approaching the functionality of a true tablet. The Apple and Microsoft tablets will be capable of decent book presentation, but will also play back TV, movies, music, web pages and hybridized print media. Movements of your finger (in fact, many fingers) will be registered in realtime, and if it gets too dark, you'll be able to bump up the brightness without the screen suddenly looking like a 1930s movie-house ticket booth.