They are very bitter!
I experimented with them. Leached and then roasted, they are actually quite bland. They stay soft even after being roasted.
They are high in protein and would, in a severe pinch, be a nutritious additive to soups, sauces, porridge and stews. IMO, they should just be ground into meal before using.
It does take some time to prepare them. They shrink inside the shell if left in the sun for a few days. Out of their shells, they look like small peanuts. I leached them over a couple of days and then dried them in the sun. I did use the oven to roast them.
The blue jays spend most of the summer eating them and hammering the excess into trees for later. I think the squirrels and woodpeckers eat the blue jay stash, though.
You have to leach them, as I recall, from cub scouts.