ePub technology in it's most layman analogies, is the mp3 format for ereaders. The nook supports it the kindle does not
now what does this all mean? It means you can shop around at various ebook stores and ebook clubs since basically all of the them sell books in the ePub format. For example my wife is a member of the kobo ebook store and she has been getting 30% coupons pratically all this month so by her owning the Nook she is able to shop at Kobo and take advantage of it's promotions. You can not with the Kindle.
Also library's use the ePub format, yes you can actually check out ebooks from the library. And so with the nook you are able to take advantage of this. The Kindle you can not.
Now the Kindle Krew will chime in and say they have no problems buying books from other stores and checking out books etc etc. What most fail to include is you have to strip these books of their DRM and convert them to amazons format. Which sort of brings up the issues of ethical and legal matters and how easy it is to do it. For some it's easy for others its too complicated to be worth it. Let alone the legality issues.
Both sell accesories such as night lights etc.
If you have a Best Buy or a Target in the area you should be able to get a hands on with the kinlde.
The nook just had another firmware update just last month which added speed to the page turning, it darkend up the text so the contrast appears much higher.
Just something to keep in mind when the Kindlebots

start chiming in about how fast the page turning is or the Pearl Ink screen yadda yadda.
Also you may hear year old nonsense when the nook first came out with it being slow etc. Since it's inception it has gone through a total 5 firmware and software updates, some that fixed old bugs, some that added features and some that enhanced performance.
Trust me when I say it's fast and responsive
After playing around with the two I honestly feel IMHO the nook is the best overall value to performance and the fact that it supports ePub puts it above the kindle.
but I'm sure you'll get an earfull from the Kindle crowd as well
Good luck.