I just read the latest test of power supplies. What suprised me a little bit is that the article is entirely focused on output, assuming the input is OK. In reality, the mains power in many cases experience voltage dips, surges and short losses of power. I bet the power supplies were to perform even worse if you tested them at the extremes of the input interval. A power supply that claims input 100-240V should work all the way from 90V to 264V. Does it?