I began messing around with tire pressures last year, and experimented in earnest starting this year.

I'm 170 lbs and both my bikes are 28 lbs. My primary bike, an '06 Trek Portland, gets two-thirds of my miles, and in the three-seasons runs 28mm Bontrager Race Lite Hardcase. The Hardcases include some sort of "anti-pinch flat technology", whatever that may mean. Yellow Bike gets the remaining one-third of my mileage, and runs 25mm Continental Ultra Gatorskins.

I found the sweet spot for the Portland to be 70F/80R, although on grocery day I add more to the rear to carry the load. On Yellow Bike, it's 80F/90R.

On both bikes, the ride improved tremendously. And neither bike seems to suffer for it in the speed, perceived effort, or coasting departments.

No flats either, despite hitting some pothole edges that I just knew would pinch-flat. They didn't.

Encouraged by this, on the new wheelset I just bought for the Portland, I went from 19mm wide rims to 24mm wide rims. The buzz on wider rims is that they yield a wider tread profile and the increased air volume allows lower pressures. Using the very same tires and tubes, I'm still experimenting, but I'm currently running that bike at 60F/75R, again finding improved ride at no perceivable loss in speed or coasting.

FWIW, Velocity's new A23 rim is supposed to provide this same improvement for users of 23mm tires.

YMMV.