These rotors are pretty light and work well enough.
Weakness:
They seemed to warp and bend a little too easily. The big weakness is that they lasted just over a year. I often ride in pretty wet conditions and brake hard. I used sintered pads with XT brakes and the Galfers lasted about a year before they were a bit too thin.
They work decently but the lifespan was too short. I had the older style years back and they cured My Juicy 7 turkey warbling. The old design was just wavey without the holes.