Well I am not optimistic that the noise will be gone. I went by the dealer and shot some pictures of the top of the head, cam phasers, chains, etc. My theories are this:
1. The oil pressure in the lifters is a little lax at cold temps causing the rockers to be rather noisy. As the oil warms up and flows a little better, then the lifters (including the one that tensions the chain between the two cams in the head) pump up a little tighter and remove slack.
2. The previous OHC engines had urethane of some sort on the main chain guides. This engine does not appear too from what I can see looking into the timing cover. It appears that the chain-guide contact is metal to metal. So when the engine is cold and there is a little more slack in the parts, the noise is actually the chains banging against the guides.
3. The design of the rocker arms is a little different on this engine than my previous 4.6L. The contact patch of the rocker arms to the valve stem was a U shape which in essence centered or "locked" the end the rocker in place on the valve stem. On this 5.0, the end of the rocker arm is a flat piece of metal that sits on the valve stem tip. The noise is possibly the rocker arm rattling against the valve stem until one of the previous occurs (engine warms to take up slack).
Whatever the case is, it does not explain why only a handful of cars thus far (that we know of) have the problem. It definitely sounds like slack in the valve train..... just which part?