I have a Kindle 3 Wifi, rather than a Nook, but I just wanted to throw my hat into the "Who needs 3G?" ring.
When I was using the Kindle 1, I mostly bought books when I was home, where I have Wifi, and browsing on it was mostly a novelty.
Wifi is anything but ubiquitous in my area, so if I felt the need to buy e-books outside of my home, I'd go 3G. But that's yet to happen for me.