gregjones, I recently discovered the same as you about tires: pressure makes little discernible difference in effort but a noticeable difference in comfort. I've also gone to much lower pressures. I think my rear was down to 50 this morning. I pumped both up to 70. These are 32mm tires on a 40-lb bike. I weigh 170 lbs.

However, I am unusually sensitive to chain friction, which I think is lucky. It keeps me oiling and wiping my chain.