I really like the cast iron grate in my Q200, all of my future grills will use cast iron. It gets hot, retains heat, and imparts nice sear marks.
However, even though it is porcelin coated like all Weber CI grates, my Q200 got some surface rust during December/January while it sat outside without a cover. About 15 minutes with a stainless brush cleaned it up (I probably could have skipped this, but I also wanted to clean up some gunk between the bars). I sprayed on some canola oil and let it heat up for 15 minutes. After that it was back to normal.