I agree that the single shot approach in YOLO was pretty clearly a big step forward. In the two years since though there much of the efficiency work has been in

I agree that the single shot approach in YOLO was pretty clearly a big step forward. In the two years since though there much of the efficiency work has been in the underlying feature detector architecture, which as you point out should integrate well with the YOLO9000 training improvements. It's very cool to see this kind of capability get within range of phone-sized devices.