Nail on boxes can be a pain as the nail bosses can get in the way of the first layer of rock. We do alot of log homes. In interiors we find a problem even with 3/4" T&G wood where the carpenters have to notch the back side of the boards because of the boxes.
1900 boxes with plaster rings is a no brainer.
"Anyone who has never made a mistake has never tried anything new." -Albert Einstein
I consider these boxes to be one of the best new products I've seen recently. I'd recommend them for any place where you're not sure what the final wall thickness will end up too. They're great for Kitchens and Bathrooms that might get a backsplash, or Tile, or whatever, very easy to adjust.
As an addenda to Sparky's post, the Arlington extensions as pictured are, to my knowledge, the only ones that are currently UL approved. They are made by other companies, but don't have the UL. Bill, very neat box!!...S