I'm enamored with the concept of having an outdoor wood burning oven. Friends of our purchased a house that had one. They used it sporatically at first, but have since abandond it. The biggest complaint is that they have to start the fire first thing in the morning and tend the fire through the day in order for it to heat the brick mass to the point where it holds the heat. The second issue they have is a simple design flaw in that the door opening is a really tiny oval, probably no more than 12" long and about 8" high. Not only does this limit what you could put in, but made tending the fire difficult.
I've seen other articles that claim that they can fire up their oven in 2 hours. I would love to hear other's experience and thoughts.