I thought I'd add my two cents to the recent discussion about Kindles. Now, I've never seen a Kindle, or researched other readers, or even thought about getting one. But mostly that's because I already have an excellent solution - my XO. Plus, the money goes to an organization I believe in to help all kids have access to computers. True, the XO is marketed as a computer, and it is actually a computer (so if you're reading a paper and discover you should probably also be reading a paper they cite, you can go get it), but I find it most useful as a reader. Once you download a paper (from the web or a USB drive), you can flatten the computer. The screen is high resolution and easy to read off of even in sunlight, since you can turn off the backlight (a feature I wish all computers had). And you can rotate the screen... though I don't really know why you'd want to. Most importantly, since it's an actual computer, it doesn't have any of these strange PDF compatibility issues - it just opens the PDF.
Sadly, the folks at OLPC seem to have decided not to run the give one get one programs that give the public access to the XO during the whole year. Based on the past two years, these happen only in November and December to capitalize on the Christmas shopping season. But keep your eyes out, because in 2010 there's promise of a super cool new design and a reduction in price. Currently, the laptop costs $400 through their G1G1 program, $200 for the laptop, and $200 a tax-deductible contribution that gives a laptop to a child without access. I've thoroughly enjoyed reading in coffee shops with mine, knowing that if someone spills coffee on my computer it will probably still work.
Of course, my XO doesn't do some of the things that the Kindle does, like let you easily pay $10 for each book.