I played with the nook at B&N earlier today, and was pleasantly surprised. While it was slow, I didn't feel it was enough slower than the Sony units I've seen to make a difference. The unit as a whole I was rather liked - aesthetically it was good, and the casing and weighting was nice.
I also was pleasantly surprised to find that while the LCD's cover flow mode was nothing like the iPhone, it is certainly usable.
If I didn't want a bigger screen I would definitely consider the nook an excellent entry to the ebook reader lineup.