I've eaten in a couple DDD locations...

Jefferson Diner in Jefferson, NJ: this is a good diner, but it's just a diner. I wouldn't go out of your way to eat here. If you were passing right by it though, it's a reliable place to get a tasty meal.

Red Arrow Diner in Manchester, NH: another place that's just a good diner. Although they have homemade desserts that look good.

4 Kegs in Las Vegas: we came across this place unexpectedly, I noticed it and said "hey, isn't that the place from DDD?" so we stopped in. It's definitely a dive, but the food was delicious.

I may have been to a couple other places without knowing they were on DDD as well.

My brother is a HUGE fan of White Manna in Hackensack, NJ so I'm sure he would recommend it.