I registered my NookColor today, and played with it for about an hour at Barnes and Noble. (I was surprised to find I could use "read in the store" to read my own books there-- I thought that feature was only for actual paper books. My novellas are probably short enough to read in an hour if you're a quick reader, so I'm not sure I'm thrilled with that. But they do have a nice BUY NOW bar at the top, so that feature might just sell a few books, who knows?)
Anyway, overall I liked it. It's very pretty, to be sure. The colors are bright and everything is very clear and sharp. It's heavier than you would expect, but I'm used to the DX, so that wasn't really an issue for me (if you're used to the smaller Kindle you will probably have to adjust). The touchscreen is generally responsive, and the interface is easy to figure out (as opposed to the original Nook, which made me go huh??? every time I played with it in the store). I didn't have to consult with the little start-up guide to make it work-- it was user-friendly and more or less idiotproof:-).
I did have a recurring problem turning pages-- most of the time pages turned easily and rapidly, but every so often it would hang up, and I'd wonder if I hadn't hit it right, or if it just didn't like how quickly I turn pages. Once I managed to freeze up the entire device by tapping the screen too many times, but that was quickly solved by turning it off and on again. It could be I'm doing something wrong; more experience with the device may prevent this problem.
The big issue is that the LCD screen did give me a headache after an hour or so of playing around. I can't see myself reading heavily on this device-- I think my eyeballs would explode. But I never really intended to use it for that anyway-- I figured it for more of a newspaper/magazine reader. And I have middle-aged eyes that need bifocals, so this may not be an issue for others.