As you can see, Barnes & Noble boasts a lot of Nook's on-paper advantages, not just a second screen and Wi-Fi, but native PDF support, an SD card reader and a replaceable battery. B&N also points out that brick-and-mortar means try before you buy. Lending between friends is downright awesome, if it works. And a huge advantage is being able to read books on your PCs and Macs. I own Kindle books, but as I currently don't have a Kindle, the ownership concept is a little bit abstract.
There are some more vague advantages: What exactly does an Android OS do for the user in this split-screen unique device? And what early adopter really sweats the dilemma to go with colorful back covers or not?
The truth though is that not much here makes Nook look bad. It's a little fatter than Kindle 2, but it's also substantially shorter, which may be a more significant physical advantage. Max battery life is 10 days, rather than Kindle 2's 14, but we still need to know what that means for the LCD screen. There's no text-to-speech, but maybe B&N just wanted to avoid the lawsuit Amazon got hit with, because the text-to-speech wasn't accessible to blind people. And darnit, no support for Word documents. Guess you'll have to Save As... PDF.