I've been wearing my Sport for over a year now (since last June, 2015), and my watch face has no scratches. This is despite a 4/day per week gym routine with weights, a good deal of travel by train, plane, and automobile(!), and general life.
I guess your experience may vary. I read a lot of threads on here where customers were frustrated with how easy the Ion-X Glass scratched easily.
I think it depends on what the Ion-X Glass is subjected to. I originally had the Sport Watch and upgraded to the Stainless Steel with Saphirre display. Your mileage may vary.