Remember the part of your grill you interface with the most is the grates. They can make or break the cooking experience. Junk grates on a great grill gives you a grill you will hate. Great grates (like Dave's) even on a not so top line grill will result in a grill you will enjoy. If all you want to do is "flip" a grill than no his grates are not worth it. But if you want to have a "keeper" they're worth every penny you spend. Because it's what your food touches, it's what you work with, it's what makes your grill "feel" like a great "tool" in your hands or something you tolerate.
As for the photos of those stamped grates shown earlier. Many were mistakenly calling porcelain coated stamped grates stainless. Specifically the ones showing rust on them. The old grates Weber made were stamped 304 grade so they did not rust ever.
One advantage of the stamped grates is they could be flipped over (I saw this recommended by Weber) to "channel" grease away from dropping directly into the flame area. Much like those expensive wood fired Santa Anna grills you see with upside down V grates.