What swayed me over was
Touchscreen, swyping makes for a more book like experience, plus the dictionary on double tap is priceless.
Screen is just as good as the kindle, wich kept me from buying the 600, and decided me on the 650
Open Format I like it to read anything I throw at it
The biggest factor was the memory card, as I want to be able to read manga, and want to be able to use the expanded storage. Kindle has no such option. I may have overlooked the rest, but no way to expand the memory was a deal killer for me.
Bonus ... Its prettier than the kindle
personal bias, but still.