My wife got a Nook for her birthday two months ago and she loves it. You should consider it over a Kindle, weighing the following observations:
1) The "next," "previous" page buttons on the Nook have a bit more resistance and are recessed beneath the unit's top layer of poly-whatever. This means they are harder to hit accidentally, and will never get clogged with hair or finger grease or whatever. See, if the "next page" button goes out on any eReader, its instantly useless. I love the Nook's design on these.
2) Similarly, the touch screen below gives you better options for reconfigurable nav of the store, and won't clog with crap. The big keyboard on the Kindle just seems cruddy to me. A color LCD touchscreen is cooler, and let's you see color book cover art.
3) Not sure on this, but Barnes & Noble might be a better negotiator of eReader book rights and prices with individual publishers. Amazon is having spats with certain publishers more and more.
4) Nook lets you lend a title to another Nook user for two weeks.
5) Dave Barry wrote the included quick star user guide. I laughed.
Hate to sound like a sales guy. The thing is sitting four feet from me right now, and it's pretty damn cool, I gotta say. You can upload your own PDFs to the thing too.