Extreme Programming (XP) with customers

I am reading up on Extreme Programming (XP) and noticing that the customers/project owner basically has to sit on your lap while you develop the system.

For people who are experienced within this methodology, how did you manage to include customers to a large degree without it haltering your workflow? To me, it looks like the customer will always interrupt you. And what good and bad experiences do you have with XP in this regard?