If you're considering a tablet, then you might consider this one
, because it will use a transflective LCD called "3Qi" by Pixel Qi. I haven't seen it in person, but at least I think it should be better than an iPad when in the presence of sunlight, and there should be plenty of apps available related to image rendering and document viewing. I am quite sure it won't be as good as e-ink in terms of contrast and eye comfort, but it will be color and there will be many more software options available. It won't really matter what OS you are running on your main machine, unless you absolutely must manage all of your media through itunes.