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)