Ultrasonic pest repellers

Anyone use them? How have they worked for you? I plugged a couple in last Monday. I have seen fewer spiders, and no earwigs, since then, but they're not all gone. The spiders in the basement weren't bothered by the repellers, so I sprayed them. I know you're supposed to give them at least a couple of weeks to work. Spiders are stupid, and it might take them a while to give up and leave.