I went ahead and purchased a 900 today at Best Buy. Best Buy had a tiny display set up with a 300 and a 600, neither of which was turned on. They had the 300 and 600 models locked away. Over to the side they had a cheap cardboard didplay for the 900 and two boxed 900 models. Not a salesperson in sight, not that they would have known anything about the 900.
At any rate I'm currently charging it up and hope to test it out with my PDFs later this afternoon. I briefly played with it and viewed an ePub that was included and it seems rather impressive. I think the screen is better than the 600. The feature set and the included accessories certainly are better and worth the extra $100 over the cost of a 600.