I find it funny how many people who respond here either do not read scientific papers at all or did not read or understand the OP's first post.
His (and my) problem is simply that we need to scan through tens of papers to look for certain key content. After that it's easy to zoom in and read the details.
Often we download 20 papers and read only 2% of the content after skimming through them in 10 min and identifying the descriptions of a specific method or such.
However the skimming through papers requires a full page overview and a good rendering of the fonts. That in turn is much better with a higher resolution screen.
All the suggestions of "buy a kindle" or "download good reader or any other pdf program" or "you know you can double tap to zoom in" do actually not address the problem at all.
I have shown the iPad (and other tablets and computers) to dozens of colleagues and they all have the same problem. We all still print out most of the papers and skim over them to identify whats relevant for us.
The only solution I can see is a higher resolution screen. On top of that it may even be better to have a 12" high res. screen but that is not going to happen anytime soon and I think a 9.7" high res. screen would be sufficient to go paperless.