Flavor wise they seem to me a cross between an onion and garlic. They can be eaten raw or cooked, I've even sauteed the whole thing(bulb with leaves attached) but that can have the same effect as beans on some systems!
My favorite way to use them is remove the outer layer of dirt and root, then slice and dehydrate. They make the cutest little "onion O's" and store well in a plastic bag for a year or two (if they last that long) I use them in soups, stews, sloppy joes, omelets, as whole rings or crushed in my fingers. My daughter already has her request in for her share.
Enjoy the woods, but please remember to harvest responsibly. Leeks have roots but are also attached to (I think) a rhizome which connects groups of them and helps them spread. To not disrupt their system, I use a garden fork to loosen the clump, then hand pull several of the bulbs, leaving a few to nourish the mother root, firming the loosened dirt back in place with my foot. As I write this, I'm thinking I really make work out of the process, but I've been picking this way for years and not disturbing the other wild flowers around them.