Matt, that's all great and correct info, but you are talking about the 5.4L 2 valve. We are telling him to avoid the 5.4L 3 valve. Those are the plugs pictured above. They are a 3-piece design, the threads, bridge, and porcelain are all separate pieces, and the dove-tail around the bridge lets carbon build up. When that happens the plug gets stuck and breaks when you try to remove it. The threads and half the porcelain come out and the bridge stays. There is a tool to get them out, but it's still a huge pain.
Additionally the 5.4L 3V has a variable cam timing system that works well below 75K miles, but becomes unreliable and noisy above 100K and is expensive to repair. The VCT system will make the engine run poorly or not at all when not working correctly and a loss of oil pressure can make it not work correctly. Also, the 5.4 3V is prone to bottom end failure.
It has the same issues with exhaust manifolds that the other Triton engines have, but the width of the engine makes replacing the manifolds much more of a chore.
All around, it's kind of a dud of an engine.