So...pomp, circumstance, history of B&N as the "real" innovator when it comes to bookselling. And then the Nook.
First, the obvious. The name. Obviously, "nookie" jokes abound. And the official name is "nook", not "Nook" - lowercase "n". That said...nobody thought Kindle was a brilliant name either. And I am not using the lowercase "n" - it's confusing.
Moving on: What features does this thing have?
Like the Kindle, the Nook has a 6-inch e-ink screen. Their reading areas are completely identical. The Nook, however, has a color touchscreen where you can view and navigate your library by book cover.
As far as downloads are concerned, the Nook relies on AT&T 3G for most downloading. However, if you happen to find yourself in a Barnes & Noble store, you can take advantage of the free wifi there.
In fact, one of the most compelling aspects of the Nook is its interoperability with the physical world. While in a B&N, you can read an entire ebook - just as you would a physical book, in the cafe or sprawled on the floor - because B&N will stream that book to you via wifi.
You can also LOAN BOOKS TO FRIENDS. And they don't even have to have a Nook - you can share your ebooks for up to 14 days at a time, sending them to iPhones, iPod Touches, Blackberries, Motorola smartphones, a PC or a Mac. Just as you can share physical books (and demand them back), you can do the same with ebooks.
As with the Kindle, the Nook allows for bookmarking, and syncing among devices. So if your battery runs out or you forget the thing, you can pick up where you left off on your iPhone or Blackberry or other supported device. (In my mind, this is an improvement over the physical world - if I lose or forget my book, I can't just pull another copy down from the cloud; I actually have to go and buy a new one. Or wait till I get home. God forbid I should have to wait. That's just asking too much.)
The Nook holds up to 1500 ebooks, and an expandable memory slot allows for 17,500 more.
But one of the greatest features is portability. Meaning users can "side-load" (makes me think of "side-along apparition" from Harry Potter). You can transfer PDFs and EPUB files to the Nook from your computer. Why is this huge? Because you can borrow EPUB books from the library and load them onto the Nook. You can load business documents (converting books from Word to PDF is so easy these days!). You can use the device for ALL your long-form reading, not just some of it.
Which brings us to the issue of content. B&N offers over a million ebooks (half of which are Google Editions of public domain titles, but half of which are not). Additionally, newspaper and magazine subscriptions are also available.
And as noted previously, in January B&N will be offering blog subscriptions via Bloggapedia - over 8000 blogs, hand-picked and curated, categorized into a great taxonomy for easy browsing. (If you haven't registered your blog with us, please do!)
As to whether or not this is a Kindle-killer, it is of course too early to say - the Nook is not yet on the market. But given the way the device is capable of handling real-world interactions - with the physical store, the library, the user's friends/family, and other devices - I'd say Amazon has a bit of catching up to do.