It felt more stressful, efficiency be damned. You spend more time at the "front" of your line (A,B,C) , waiting for the board to change. In a traditional system you can hook in behind someone and "zone out" / chat with your SO until you reach the register. In this system I felt like I had to pay attention the whole time and I was interrupted every time the bell rang, even if it was A's turn and I was in line C.