A few months ago I bought a Kindle DX, but after the initial excitement I find I have barely used it. Partly this is because I still have a preference for paper — in particular, I find myself flipping around a lot when reading papers and the Kindle, at least, did not handle this well. But I also quickly became disappointed with the Kindle itself. My dream was to load a library of research papers (and monographs, etc.) onto the device, and then have ready access to them whenever I needed to look something up. But, amazingly, the Kindle has no support for directories meaning that if you load too many papers you have to navigate through screen after screen to get to the one you want. (A few months ago, Amazon announced a plan to eventually support directories but I haven’t heard anything since.) In addition to this, I just didn’t find the Kindle very convenient to use: the delay when “turning pages” was noticeable, and I found the buttons clunky. (I’m not the only one.) Finally, the contrast for pdfs is lower (thus harder to read) than the contrast for native Kindle content. In particular, I found it hard to read in the dim light on an airplane — one of the exact times I would want to use it.
I expect, with time, all these issues will be fixed. Perhaps they have been fixed already — can anyone recommend an e-book reader specifically to be used for reading research papers in pdf?