I haven't been through customs in about 5 years, but I remember the passport control in CDG being a piece of cake. I think the agent took one glance at my passport and let me go.

Coming back to the US was a lot worse. I can't remember if I was asked any questions. Do the CBP agents commonly ask questions to US citizens?

One thing I do hate is having to collect my bag, recheck it, and go back through security. I guess security in non-US airports isn't good enough for CBP/TSA standards.