I have a k1, k2, k3 and iPad. In fact, I brought the k2 and k3 and iPad on a vacation with me to Kauai. Don't try and read complex PDFs on a kindle. I have several dozen downloaded onto my iPad (dropbox+goodreader make this trivial) - the kindle is not the right tool for flipping through PDFs. I have logged about 40 hours reading on the kindles in five days - (mostly on the beach, a little at coffeeshops) - but linear text reading (novels) is really their strong suit. I don't think I've ever run into anybody that tried to use them for technical/reference/diagrams and was happy with the results. Too slow, no easy way to hop around in the doc.

The iPad, on the other hand, is almost perfect for this. The screen needs to be higher resolution, easier to read in sun (though a matte screen protector helps a lot) and I'll be perfectly content.

As it is, I have not printed a single 8 1/2x11" printout in six+ months - the iPad has let me go almost 100% paperless. (11x17 printouts of network diagrams still useful in meetings)

Still you have to wait for the page to render. When you are turning a page in a book or a printout you are doing something that requires some kind of activity from your part, but when you have clicked the button you are just waiting for things to happen.

I don't mean to say that this is a big problem, and I haven't been using E-ink readers that much. But when it comes to digital reading, I appreciate the snappiness of scrolling fast through pages and also the "jump to" functions, whether it's via links or "go to page" actions.