The HP iPAQ 210 looks like a wonderful PDA --- I wouldn't mind having one! The problem with a PDA is the battery life --- you pay for that gorgeous screen. I've read a review that says the 210 can get up to 7 hours of "heavy use" on a single battery charge, but I'd be a bit skeptical of that. Using it as an ebook reader, I'd be surprised if you got more than 3 hours of continuous reading.
At least that was the case with my Tungsten E. There is enough to read in a screen full of text so you won't be too bothered by "flipping the pages." Although I must admit that my thumbs get cranky after a couple of hours of page-turning. As far as "eye fatigue" goes, I never had much of a problem reading from the Tungsten as long as I was wearing my cheap reading glasses, other than some "watery eyes" late at night which indicates that I should have turned off the lights about an hour before
That's what happens when you turn fifty...
I love the reading experience on my Sony PRS-505, though. The time between charges is immense (compared to a PDA), and the text and background are very easy on the eyes indeed. No problem reading in bed: I prop it up like a tent, bring my fingers out from under the covers to turn pages every now and then --- and I can read just fine with the 60watt bedside lamp (even turned away from the light!).
So....my recommendation (if you haven't guessed already): You need both!! The iPAQ 210 PDA makes a very passable reading device for short stints (such as lunch breaks, waiting room waits, etc.), and has all the added bennies of calendaring, etc... and a beautiful color screen. But for serious e-reading, where you are wrapped up in a book and just can't stop reading, nothing beats a dedicated ebook reader, be it a Sony, Kindle, Iliad, or whatever.
So start saving your pennies, my friend. The Sony can be had for $269.00 and the iPAQ 210 for just over $400.00, if you know where to look... (Google)
Good luck!
Tim