Just make sure that the LAN 767 really has the latest business class seats. We did some flights with LAN in south america this spring and I remember reading that LAN had finished the business class upgrades on their 767 fleet. Unfortunately that was probably just LAN Chile as our LAN Peru flight from Lima to Buenos Aires had the awful old seats.
We haven't had any problems with the Madrid airport and the Iberia flights from Madrid to both Buenos Aires and Santiago de Chile have been just excellent.