"two words: battery life
otherwise i'd totally agree with you,and it's a good point.
on trips of two days or less i just bring my cell phone"
I used my Droid X on a 5 month trip this year, and battery life was not an issue. I just carried two spare batteries, made sure all three were charged each time I'd leave a trail town, sit next to a wall plug when eating in a diner, etc --- no problem. No solar charger this trip.
I acknowledge that it depends on a person's backcountry 'style' --- less hiking and more camping would mean more time to sit and use the device and potentially run down the battery(s). But at just over an ounce per battery, not a really big hit there, and again --- I would likely be carrying a cell phone anyway, so ... !
I'm not trying to knock eReaders like the Nook or Kindle; it's just that for me personally a device that's primarily designed to read books isn't the optimal thing to carry on a backpacking trip --- not when I can get a "pretty good" reading experience with a more generally useful device.
I should also acknowledge that I rarely read when backpacking --- do my camp chores and then sleep. So perhaps my comments are out of place for this particular thread ... though I do read a fair bit on my phone in other contexts (in trail towns sometimes, and even at or around home).
In any event, I definitely don't mean to lead the discussion off track or disparage folks who see things differently!