This show was first shown on NBC for 3 seasons, and is now continuing on TLC. I'm happy that they're continuing without much decline in the production value. I doubt it costs much, and the most important ingredient are the celebrities.
Each episode, one celebrity investigate his/her ancestral history usually concentrating on something they're interested in. That's really the only rub I have against this show. The celebrities could certainly hide things they don't want to air in public. But most importantly, they might be interested in a really boring ancestor.
That doesn't happen a lot. Most of the discoveries are quite fascinating. Not only does it reveal personal history, but sometimes it reveals little known world history events. It brings the past worlds to life in the most personal ways.