As a young'un my grandpap would take me gathering nuts. He knew the location of many nut trees and berry bushes in Western Pennsylvania, Northern West Virginia, and Eastern Ohio. Few people collected wild nuts at the time (and fewer today, I imagine), so my Pap would often bring home bushels of nuts, especially black walnut.
I've only tasted the butternut on a few occasions--the trees were not so common, and did not yield fruit very often. I remember at least one time eating butternut cookies. And since I've never seen butternuts at the supermarket, I'd venture to guess that most Everythingians have not tasted butternut. So personal anecdotes being done with, allow me to describe eating a butternut.
First there is the greenish husk, which can be stripped to reveal the shell (which looks much like a typical walnut). After handling the nut, you will notice the smell on your fingers. It smells like butter, though not quite. I remember the scent as akin to the buttery topping of movie popcorn, although not so cloying and artificial. The meat of the butternut looks like other walnuts but almost drips with a rich oil (hence the name, of course). Nutting, to nut, I recommend it.