Amazon's Kindle DX has a 9.7" e-ink display with 1200x824 pixels, 16 shades of gray, and faster page transitions. 10.4 inches long and 7.2 wide, it is 0.38 inches thick and retains the basic capabilities of the standard model: EVDO internet and the Amazon store.
New features include native PDF support and 4GB of storage, two line-items that Sony's Reader can no longer claim as advantages over Amazon's model. The Kindle DX also does automatic orientation adjustments when you rotate the tablet, like the iPhone and other accelerometer-equipped gadgets.
The giant screen does it for me. The price -- $490 -- is a challenge.