3. pdfs that have been scanned as images? Does the zoom reset on each page turn make this non-feasible?
4. pdfs of articles printed from a web page - i.e., if I see a long article that I'd rather not read on my computer, I was thinking I could print it to pdf and read it on a reader. [/QUOTE]
I think all said above is true.
3. Zoom resets on each page turn. But if you're talking about something close to magazines, I see that point as a benefit rather than a set back. With ads or different layouts per page in a magazine, resetting the zoom level on page turns will give you an overview over the next whole page so you can decide on where to zoom in.
4. I've heard about online services that specifically "reformat" blogs and put them into files. The files can be set to the specific device you own. I don't have any of their web addresses at hand, but a quick internet search will give you some results.