Bike weight matters, just not to the degree that some folks would like to believe that it does. It matters when accelerating from a stop, and climbing up a hill. On flat ground, I'm not gonna say it doesn't matter at all, but... it doesn't really matter at all. Up there past 22mph or so, aerodynamic drag is so much more significant than weight as to make weight insignificant. And going downhill, more weight is always better. Mostly.