The celebrities are rarely the interesting bit - it's the insights into social history, how people are rarely from where they think, and how stories of one family can illuminate history that are so fascinating.
Though sometimes seeing some celeb you thought was a twit being really interesting, or vice versa, adds something. Alan Cumming's story was one of the best dramas I've ever seen (and then his autobiography added even more to it).
Kurri I saw him in Godot too and it was amazing - it's a play that's all too easy to do really badly!