eInk is a mixed bag or pros and cons when compared to a backlit glossy screen.
Backlit screens have a marked loss of contrast outside, to the point that some become illegible without being turned all the way up, which drains your battery. Inside, in rooms with multi source direct light, the glare on a glossy screen can lead to significant eye strain. With an eInk device the more light the better the contrast, which means outside or a well lit room, you are going to have an excellent experience without adding strain to the battery.
Battery life on an eInk screen is many orders of magnitude better than with an LCD. The iPad's battery is exceptional, and gets about 11-12 hours of use, but a Kindle or Nook can (with 3G off) can literally go weeks between charging.
Finally, there is some significant evidence that prolonged use of LCD screens even in the best of situations can lead to eye strain, certainly much more so than with stationary type or eInk.
On the other hand, most eInk does not have a backlit option whatsoever, which means you can not read in the dark. Say what you will about how much the regular person likes to read in the dark, there is without question utility in this.
The refresh rate on eInk is extremely long compared to an LCD (one of the reasons for the better battery life), which means for doing anything other than reading books (web browsing, multimedia, etc) the device is very near useless. That must factor in the cost-benefit of the device. Which is to say, even though it costs half as much as the lowest end iPad sku, it is capable of doing less than half of what an iPad can do, which means the pricing is not as far off as you might imagine.
All of which is to say, that an eInk device is tuned for reading books. If that is your goal of a device, it is likely going to serve you better. That said, if you are prepared to compromise on that experience, the iPad will get you further if it is the only supplemental device (it still requires a computer of some sort for full funcitonality) you have.