Amazon has just announced native PDF support for the Kindle 2, which is good, and the stuff we have at
www.pdfplates.com work on it. Hugh is correct, though, that the screen is much smaller, and older eyes may not be too satisfied with it. There are some pics here of PDFPlates on the Kindle2.
http://twitpic.com/qwb3p
and
http://twitpic.com/qwb9o
As for the screen saver issues, the new firmware released today changes the timeout to 20 minutes, and there are hacks you can find to set that wherever you like. I have my DX set to 60 minutes.
The Kindle's navigation isn't as good as the sony. But one advantage the K2 might have over the DX is that it has dedicated number keys, you don't have to hold down the shift key. For what it is worth, Amazon does have a generous return policy so you can try for a little while.
Seems like everyone is coming out with an eInk based reader these days. There are so many choices, and by first quarter of next year there will be even more.
Feel free to drop me a line, admin<at>pdfplates.com with any questions.