Maybe you can't feel the difference but I think I can, even at my puny weight. It's not a night and day difference, obviously. I calibrated my pump using an electronic pressure gauge and it tends to be accurate within +/-5 psi. It's just a department store pump with a plastic gauge on it and it's been working fine for years.

I realize there is a point of diminishing returns and experimentally I would put it at 120psi. Depending on the tire and on the road (and the rider, and wind, etc...), 10psi fewer DOES make a difference.