If the advantage you like most about an e-book handheld is that you can have your books with you where ever you go, that same advantage is offered by any handheld or portable digital device because they can all run e-books.
If the advantage like most is the "e-ink" type screen, then that has nothing to do with the e-book reader itself. Display technology is evolving quickly these days and it won't be long before all portables and handhelds have qualities that closely match the e-ink displays, but can also do color and video. For instance, the kindle's screen is 167 ppi resolution, and the new hi-res screen option on the 17 inch MBP is now at 133 ppi. Higher PPI resolutions will now quickly filter down to all handhelds.
What is the advantage to a dedicated e-book reader? Who wants another single-use device to lug around?
Good, now combine both qualities into a single device and the combined reason is why I'd like one (but wouldn't buy one until prices drop). There's no point separating your two reasons. I wouldn't want to read documents on a PDA-type device as a long-term solution, and I wouldn't want to just open up my MBP to read the paper, regardless of the ppi. I wouldn't want to do it on an iPhone, either. The screen is too small. I think a thin device with a 5" screen would be great.
The wireless downloading capability (off EVDO, not WiFi) is fantastic if it continues to be free. I can read blogs and download newspapers from all over the world.
Hmmm.....if I commuted on the train or something, this would be amazing. For now, as a researcher, I just need to read PDFs very frequently, and it seems to be good for that, too.
Too bad about the price, and not selling it to people outside of America.