Ok, first - I use most of the 12 volt sockets especially the one at the dinette. I have a dometic 12 volt cooler I plug in there and fill it with bottled water.
I also have a decent 12 volt vacuum. Cool to have the 12 volt outlets all around (as well as the 120 volt).
In my experience with USB wires, plugs and kids - they will snap them off right at the plug point. Especially at the location under the dinette seat. My 12 volt cooler is often being kicked out of the socket.
I was going to install the multi-outlet (outlet with the USB) for the 120 volt outlets in the kitchen but thought better of it. I have a box full of 12 volt to USB adapters for most all or needs. In fact, my truck had the USB Ports but I still use the bulky adapter. Old fashioned I guess.
I like the concept but I don't see it as a "WOW" item personally.
I have plugged my phone USB 12 volt adapter into the 12 volt socket at the dinette seat and used a can coozie to hold my phone in the table drink holder. The coozie keeps the phone from bouncing around.
I will also mention that "we" totaled a tablet in a slideout - moving the slide back in, who knew the tablet was in the path. We now check the slide paths top to bottom.