I was the guy that used to write all the software for the CVap ovens at Winston, so here's my take... The basic idea is the pan of water is your food temperature and the air temperature is your food texture/browning. It really is incredibly simple technology, and it really is quite superior to the old way. I would LOVE to have that feature in a normal home oven. The same oven can be a proofing oven, baking oven, steamer and holding cabinet. You can cook a roast and it can safely be held for about 24 hours without affecting the food at all (medium-rare will stay that way no matter how long you keep it in the oven). Not to mention that is cooks faster and more efficiently. Also you can cook at lower temperatures safely, which is kind of big.
The two major difficulties are: 1) The pan of water is a pain to clean and keep full. All that moisture just builds up gunk. 2) The user needs to rethink how they cook. They need to think food temperature and texture, rather than cook X minutes at Y. It's simple to modify your recipes, but customers have always seemed quite resistant to change. I still say it is needed in every kitchen, however.
Basically, Louisville is a small town when it comes to Engineering. I had some contacts which eventually led to a job there. But the job got stale. Our platform was based on a National Semi COP8 (8-bit micro without even a multiply instruction). That can only be interesting for so long. So I went to GE and started designing 3-phase induction motors. Quite a change of pace.
It was a lot of holding cabinet stuff. That's easy to introduce into your workflow and doesn't really change the way you do things. Primarily a money saver by being able to hold things longer. I think Arby's experimented with it since they slow roast at a fairly low temperature. Cookong that way will more quickly get you out of the "unsafe" region where bacteria grows quickly. Restaurants menus have been optimized for the current way of doing things. There's not enough incentive to change that. Especially in franchises where you'd be forcing them to buy expensive new equipment and shake up the menu. (KFC is especially scared after the meas introducing the Chicken Little caused.) It's easier in fine dining and smaller chains where they have the ability to experiment. They also have more incentive to be different.
I've seen that same situation regarding chains that are trying to stay relevant with new items but trying to avoid the constant introduction of new equipment in the kitchens. When it works it works great, like you mentioned it can also go incredibly bad.
My eyes have also been opened to the politics between the corporate parent, the franchisees, and even how the vendors get involved (like Coke or Frito-Lay). It's crazy stuff.
The two major difficulties are: 1) The pan of water is a pain to clean and keep full. All that moisture just builds up gunk. 2) The user needs to rethink how they cook. They need to think food temperature and texture, rather than cook X minutes at Y. It's simple to modify your recipes, but customers have always seemed quite resistant to change. I still say it is needed in every kitchen, however.