It's awesome. Did you know that Dominican is the most common ancestry in Manhattan? That Appalachia's largest ancestry is simply "American," self-reported despite its absence as an option on the Census forms? (Nate Silver used this data to augment his election models.) That the vast national interior has German as the most common ancestry—not surprising—but Utah is mainly "English"?
If you're curious, here's the full Census brief where the map originated.