A Silca engineer, when interviewed, said that if you want to go fast you are much better off running pressure that is lower than higher. And he said this is because although there are gains to be made by running high pressure, they are much smaller than the losses that can occur from vibrations induced in the bicycle from the texture of the road surface. He said that as he and his crew were traveling around the world being technical support at races, they almost never used their tire pumps when adjusting the pressures of bicycles they adjusted for various riders, in almost every case they were letting air out of the tires they looked at.
This engineer said that the only surface that could use higher pressures would be a sanded smooth and varnished velodrome track, an outdoor concrete velodrome, although being very smooth, would not use higher pressure for optimal performance. So the take-away is that anyone riding on any sort of public paved road, is certainly better off running pressure that is low, not so low that there is any danger of damaging the tire in use, but not pumped up to the max pressure that is on the sidewall of the tire.
So I have been riding with lower pressures lately in my road-bikes, not worrying so much about them being pumped up to the sidewall pressure, but having them ten or fifeteen pounds lower. There are a few local courses I ride which have been used for time-trials in past decades, and eventually I will get round to timing myself on them while riding with lower pressures. All the science says that I should be faster with the low pressure, but I do not use any sophisticated methods of measuring, just the stop-watch feature on a wrist-watch over a dozen miles. I am guessing the low pressure will not hurt my speed at all, it may make me a little faster, and it will certainly be a bit less fatigueing, so all I see are advantages.