E-ink is a black and white display that attempts to simulate paper. It allows you to read the display even in direct sunlight without the bad glare you get from other types of displays. It also makes what limited web browsing that ebook readers have terrible.
If you want to be able to read ebooks, listen to audio books, and do web browsing to sights such as Hulu etc. I would check out the Kindle fire and the Ipad. Fire would be a “C” and Ipad an “A” in my book. But their price differentials reflect that as well.
An e-ink screen is very different from the backlit screen found on other devices. As Omar Little notes, it is designed to simulate, as closely as possible, the look of an actual printed page. (If you’ve ever played with an Etch-a-sketch, it looks something like that.) Many people prefer such a screen for reading books, finding it easier on the eyes than a glowing monitor or tablet screen, and it has a big advantage in battery life—but there’s no way you could watch YouTube videos or things like that on it, so it sounds like that’s not what you’re looking for.
eInk is a system where the pixels on the screen are physically rearranged, as opposed to something like an LCD display, which shines lights through the screen to create the image. It was initially developed by MIT’s Media Lab.
eInk is pretty ideal for “pure” readers such as the Kindle Touch or Nook Simple Touch. It uses NO power unless you are rearranging the pixels, ie, turning a page. It is “matte” in appearance and doesn’t reflect glare like glass does. So in bright sunlight, it feels about the same as reading a physical book. Whereas most familiar types of screen are LCD display, which is always using power because it is always generating light. In bright sunlight, an LCD display may look “washed out” and reflect lots of glare.
Since eInk only uses power to rearrange itself, a charge lasts a LOT longer on an eInk display. A charge lasts 2 weeks to a month (with an hour or so of use most days) on my Kindle Touch, an eInk device. Wifi does make it drain faster, but not that much faster. I keep wifi turned off unless I need it for something specific.
Since the screen uses no power when its not changing, eInk devices are great for people who encounter interruptions, because you don’t have to remember to turn it off. If you don’t touch it, its the same as being off (except that if wifi is turned on, it does draw some power all the time).
All that said, I don’t know of any eInk e-reader that offers functional web browsing.