I don't have a nook.........but I've had the Kindle v1 since June of 08.
Heres the thing. I just want to read books. At first, the wireless thing was neat. Then I discovered mobileread, and the ability to load books from the computer to the k1. From here I found other site with free books.
The lack of epub support, and library usage stopped bothering me when I learned to convert, and run kindlefix scripts.
I never use the mp3 option....I hate audio books. I like to just hunker down and read. No distractions.
The little color screen at the bottom? Thats just for looking at book covers, right? Calibre does the same thing on my computer....doesn't seem like a reason to buy one for me.
Most of all, I love Amazons customer service. Twice I've had to 'return' an ebook. Instant credit both times, no questions asked. I've used both their email and phone service. Questions have been answered politely and accurately.
As far as returning a Kindle vs a nook.......the only thing you pay for is return shipping.......no 10% restocking fee.
The thing is........you can't really tell how any device will work until you use it on a continuous basis for a while. I knew with Amazon I was out only the $10 postage if I hated it.
Luckily........I loved it.
Now.......that being said, there are lots of people here who feel the same way and love their nooks, Sony's, Aztac, Hanlins, Pocket Books, etc.
Its a decision you'll just have to make for yourself!