I got a Nook instead of a Kindle. Mainly because I could demo it in the store and see how it worked -- that's always easier for me -- to try things out before I buy. I knew I wanted to buy an ereader because I'm so sick of carrying tons (sometimes almost literally) of books with me when I travel -- once I carried a huge Stephen King book with me + several others -- that hurt my back. I'm never sure what mood I'm going to be in, so I have to take several books with me to be sure I accommodate the mood I end up in. This is tedious. Very tedious. Tediousness and lack of space was the same reason I eventually got an iPod -- it cut down on the stacks of cds I took with me when I travelled.
Do I like my Nook? Yes -- yes, I do. The screen is easy to read -- it's small but the fonts are clear and easy on my eyes. I didn't read the instruction manual (mainly because I never do) but I was still able to figure out how to operate it. I don't like that there is no option for me to set the screen to backlight so that I can read in the dark, but if I'd read B & N's FAQ on the Nook in the first place, I would have known this.
Will it replace the physical book for me? No. But I always knew that. It does satisfy the needs for which I bought it -- space for books and easy carrying of my books when I travel. Plus it has the cute little covers of the books on it.