Quantum annealing - a finite temperature version of the quantum adiabatic algorithm - combines the classical technology of slow thermal cooling with quantum mechanical tunneling, to try bring a physical system faster towards its ground state. The Canadian company D-Wave systems has recently built and sold programmable devices that are designed to use this effect to find solutions to hard optimization problems. I will present results of experiments designed to shed light on crucial questions about these controversial devices: are they quantum or classical? And are they faster than classical devices?