When Fire HD but you need enough light (on the QR code) and a steady hand, otherwise the recognition works not with the Frontcam.
Cons: After making changes in the settings, the recognition is poor, so you should briefly quit after setting changes the app and restart {to do but rarely eh}. The setup menu has not been adjusted to the tablet / Panorama mode (as opposed to the scanner itself), and therefore is on the side.
Advantages: Simple, well-adjusted, also works under Fire OS / with the Fire HD 2012
All in all, I prefer therefore from only one star (for the disadvantages).