i could see how a machine big enough for 4x8 sheets with an automatic tool changer, a vacuum table, and all the automatic calibration gizmos might be a time saver for a production shop, but if you're building something that's a one-off or you don't have all the setup automation goodies (which are $$$$$) then setup and programming usually end up taking longer than doing the work the old fashioned way.
for tenon cutting like in the bed rail example you gave, i have a hard time imagining any situation where cnc is going to be more efficient than a domino xl.