Humans love stories, and this show does an excellent job of using television to tell the stories of real people, without being maudlin or mawkish, or throwing them into contrived situations for comic or dramatic effect.
While we are dealing with the ancestors of a very select group of people (after all, how many would watch a show about *my* family tree?), the stories they tell are the stories of all of us: the former German POW who loved his time in an Iowa POW camp so much he came back to the U.S. after WWII. The story of a family torn apart by alcoholism and abuse. The story of people fighting for justice, sometimes at the risk of their own lives.
To get stories told this well, I am willing to put up with the heavy handed references to ancestry.com, and the smiling, infallible librarians and archivists who seem to always have just the right document.
Lisa Kudrow was great in "Friends" but I think this is the show should should put at the top of her resume