First, a note of explanation for new Thanksgiving cooks: "giblets" is a collective term that includes the heart, liver, and gizzard of a bird; there is no organ called a giblet. If you can bring yourself (or persuade someone else) to chop them up finely, giblets are nothing to be afraid of — and they do make a difference to the gravy.
I outsourced your question to Bruce Aidells, veteran carnivore and author of "The Great Meat Cookbook." He uses the heart and liver for gravy, and saves other bits and pieces of the bird to make stock. Here's his answer:
"I think they not only add a rich savory flavor to the gravy but wonderful bits of meaty texture as well. I use the neck, gizzard and wing tips to make turkey stock which is then used to make the gravy, along with the defatted pan juices."
However, if you prefer a smooth, lighter gravy, you can leave the giblets out and add the heart to the stock. Don't use the liver in the stock; the taste will be too strong.
