It's actually one millinewton per kilowatt, which I understand is only one order of magnitude off of current Hall thrusters. It's not great, but Hall thrusters are really useful for deep-space missions, so if this works, it could have use as a vehicle engine.
It seems it's their scaled-up estimate and that they actually measured micro Newtons, close to the margin of error of their setup? Specifically, the highest input power was 80 Watts, if I didn't miss some picture in the paper, which would give around 90 microNewtons actually produced per 80 Watts? So their summary seems to be misleading.
I tend to believe that they measured "something" but that that something has some plain explanation.
It seems that at the time the claims leaked (September) the figure was even "1.2N per MW", but still:
"For the EMdrive, the device that was tested here, thrust was consistently observed on the device to be between 30-and-50 microNewtons, giving us that 1.2 N/MW figure. But the limits of the measuring device’s threshold was just 10-to-15 microNewtons! In other words, these results may be consistent and interesting, but this isn’t as robust as anyone wants it to be."
