I was quite impressed by the speed and violence of the reaction. It was all over in less than a fifth of a second, and the cloud of smoke it created made a smoke ring at least a yard in diameter. It was quite amazing to see.
Although the slow thermite was a bit of a disappointment, it did make solid copper pebbles, which is more or less what I was aiming for. I used a hammer to pulverize the slag and then washed the mix with water to float away the less-dense slag. This actually separated the copper out quite well, and in the end, I recovered 3.55g of copper granules. This is a 9% yield, which isn't terrible, considering the thermite seemed to sputter instead of flaring up nicely. In any case, my expectations were "blown away" by the fast copper thermite smoke ring, so I consider this experiment a success.