I haven't installed one, but I just saw them do one on HGTV a couple weekends ago (I sound like a commercial for Holiday Inn Express don't I?).
Anyway, it looked fairly easy to do. I guess the panels have holes for the nails, and they interlock with eachother somehow. I'd have to really look at a panel to see how they did it. I can imagine it's pretty hard on the back/neck since you're on a ladder doing it, but they did a library and it looked great when they were done. They also used the tin/plastic crown moulding that matched, but I thought it was a bit much.
Good luck on your project!