When I switched from 38 to 28 mm tires, felt like I was ultralite.

The only time weight is much of a negative is when climbing. Actually an advantage when bombing downhill, and pretty much a wash on flats.

The responsiveness of a 15 lb load is fun. And since every pedal stroke is an acceleration, every ounce does count. Lighter the load, the faster and farther you're likely to go/day.