I can speak about this one. I originally got myself the 3G, but due to a snafu in my order, I had to go return a few at my local store. (I ordered them online and part of my order was duplicated) While I was there, the manager talked me into a NC instead of my 3G.
It's nice, I think just for myself I would prefer the 3G (maybe, the shelf feature on the NC sounds good, but I haven't really played with any of them yet), but I have an 8 month old, and I thought the read to me feature was pretty cool.
BUT...there are not a whole lot of books available yet. "Classics" like Goodnight Moon, Love You Forever, Guess How Much I Love You, etc are not available...yet. According to the salesclerks in the store (one said the NC is only 3 weeks old, I didn't know it was so new) said they are adding hundreds of books monthly, so maybe in the near future, some of those books will be available.
My advice, if you are leaning toward the NC because of your kids, is to go look through the selection on the B&N website, and see what is available for the NC specifically.
They have 2 free books that I downloaded, Richard Scarry's Colors reading comes through loud and clear, whereas I sorta have to struggle to hear Rudyard Kipling's How the Elephant got his Trunk. I haven't looked to see if there is a headphone jack on the NC, but if there is, I'll likely hook a set of computer speakers to it when we use the "read to me" feature, so we can hear it better.