The beans on the left are the medium roast from yesterday, and on the right are the beans (medium/dark) from this afternoon.
It took about 5 minutes to roast to this colour and it was very even across all the beans. Much more even than I ever got roasting from green beans in the wok.
The machine. . .
If choosing a popcorn popper to home-roast green coffee beans, make sure you select one that blows the air in from the sides of the machine not from a mesh underneath. This is so the skins that flake off from the beans don't fall back into a heating element, but also because the side-air models keep the coffee moving and give a nice even roast. It also help if you don't overload the machine.
Below is a picture of the roasting chamber of my popper and you can see the solid base and airflow ports on the side.