As boldtz said, i'm not a fan.
1. I think grill marks should be mahogany, not black. Grill Grates are great at making marks, but they always come out black.
2. The space between the marks doesn't get color.
3. Fats from the food don't make it to coals, which means significantly less fat-smoke blessing the food with flavor.
These grates do not solve any problem for me, I find them gimmicky and misguided.
That's just my opinion of course.