Ford tested these F150s for years down in the salt mines before they announced this.
Aluminum and plastic continue to increasingly be used because the gov't and consumers demand better gas mileage.
For those who abuse their vehicles and use them as work vehicles, the immediate issue is repair costs. And repair costs are different and will be higher to repair aluminum. The lights are apparently made of unobtainium as Edmunds pointed out when they took a hammer to one and then took it in for repairs.
This points to insurance premiums being higher for these.
For those who baby their trucks or want more towing capacity, this may be another step in the right direction.
No doubt this is risky and only time will tell whether it works, gets improved or it moves to other vehicles. Frankly, I would have thought this would be a better fit for cars but my guess is the towing capacity is the driving force behind it.