The good news is the PDF support on the Kindle DX works great. I haven't tried anything with DRM....
In portrait mode is strips off the margins to maximize the display area -- and since I'm nearsighted (and my eyes are getting BETTER with old age) I take off my glasses and hold it where it's comfortable. I haven't had any problems reading anything in portrait mode.
I use an M-Edge flip cover and while it adds a few more ounces to the weight, I think it makes the DX easier to hold. Since I got the cover I haven't "almost dropped" the Kindle DX.
Before the cover I felt the DX slip a few times in my grip while reading.
Rotating the DX to landscape mode puts the PDF margins back, but seems to usually still make the text larger. I just read in portrait mode and only go to landscape to study a graphic or exhibit.
The Networker's (CiscoLive) presentations are small in portrait mode -- but still readable (to my old near-sighted eyes with glasses off). I miss the color in the presentations, but the gray scale works fine for getting the point. Rotating the presentations to landscape makes them larger, but then (because of the margins) you're not seeing the entire slide at one time. It would be nice if it could scale the PDF without margins in landscape mode -- and give a "fit content to page" option.
The bad news -- yep, $500 is ridiculous for a "PDF Reader." And the web browsing is too slow to make me want to try and "get my money's worth" that way.
I gave up on Sprint over 2-1/2 years ago after a wind storm and my service at home went to crap. Plus they had the nerve to robo-call my cell phone several times a day trying to sell me a 2nd line when the 1st one wasn't working at home.... The Whispernet service is still poor at home, so it does eat into the battery life -- I have to charge every 2 days or so if I leave Whispernet on to retrieve my newspaper/magazine subscriptions. If I leave it upstairs I get a better signal and can go to 3 days between charging. I can still read then, but it doesn't have enough juice to "phone home" anymore.
I don't bother to mark or highlight my books -- I take notes on paper if I'm studying something -- so the note/annotation features aren't important to me. I'll probably read with the Kindle now (when I have the PDF) but still use the book AND Kindle when doing any book questions/exercises -- Kindle on the question page and use the book to look back at the chapter material to find the answers.
The phone texting generation may not mind the "keyboard" for notes/annotating their eTextBooks -- but you're limited on what you can do with PDFs.
The super bad news -- still no FOLDERS or anything reasonable to organize your documents/pdfs. Right now I just click through about 8 pages of PDFs sorted by name. While you may be able to someday load 3500 books onto the Kindle, if you load even 500 PDFs it's almost impossible to find what you want unless you know the name or click click click click click click a LOT to page through your directory.
The Kindle DX does let you move your Docs and PDFs into folders from your PC -- it just ignores the folder names and any structure when it displays what you have loaded.
I might try the "create a web page" trick and try to create a nested web page hierarchy I can navigate through that links to the books -- just not sure how slow the local web page display is until I try it. I'd just name the "home page" something that sorts by title to the top of the list. Plus I'd probably just move the PDFs onto a Linux System first and use a shell script there to build updated web pages as I wanted to move/remove Docs/PDFs onto/off of the Kindle.
