Galaxy Tab 7.7 (1280x800): http://mikecanex.files.wordpress.com/2012/04/techfondle04121...
NookColor 7" (1024x600): http://mikecanex.files.wordpress.com/2010/12/gbpdfs002.jpg
I don't own either of those -- or any. I'm still undecided on which would be best. [typo edit]
So depends on what your PDF is like. For basic text, the 7 inch screen was fine. For technical papers, you'll probably want something bigger.
I think I'd have to agree with OP on that one because for a month, I had to read a 2 column PDF on a 10 inch tablet and that strained my eyes to do. Would a one-column PDF have worked? Yeah, it would have, but I think just barely. I can't imagine reading a one-column PDF on a 7 inch tablet (I hate scrolling unless it's to change pages), much less a two-column one.
I was looking for PDF solutions months ago, but if this works well, it could come in handy in the future.