I tried the Jetbook Color and am unhappy with the results, even though my primary purpose is as a PDF reader. I also want a device that can use ePub and/or Mobi and can read Kindle and Google Books content. The eInk 9.7 inch readers aren't impressive as general purpose devices even if you're not interested in browsing, so I've about decided to go with some kind of tablet.
The two I'm considering at the moment are the iPad and the Nexus 10. For PDFs the Nexus would probably be OK, but the screen size in portrait orientation is about 8% smaller than the 9.7-inch screens, even though it has a 10-inch screen. That's because they've gone with the "little movie screen" concept. At any rate it would probably be adequate, which brings the consideration down to other factors.
1. What are the advantages of an Android device like the Nexus 10 over the iPad OS, or visa versa?
2. What is it that is uniquely available via Google vs Apple? Is one better at cloud syncing than the other, for instance? Kinds of formats and their facility?
I'm assuming that it's possible to do annotations of eBooks and PDFs using a virtual keyboard (not handwriting), but that's something that was missing on the JBC so I guess I can't take it for granted. I currently own a Kindle 2, but the screen is just too small to use with PDFs or to exhibit things like graphs and maps.