I like the idea of the 900, but really don't think it would be for me ether. One thing is I am somewhat visually impared, and have to have a good screen. That is really the main reason the iPad is something I look forward to seeing in person. For me the multi-functionality and the gorgeous screen (at least that is what they say) are of interest. The Nook and Kindle are pretty much the same (at least as far as I can tell), but it's great that you are taking the time to try them all. As far as a dedicated reader goes, and money no object, the Skiff looks awesome.
http://www.skiff.com/skiff-reader.html
Good luck!