I don't use them, but do read comments all the time recommending to use them. Unfortunately, they seem to be used for the wrong reasons.
The comments are for folks having issues with drips, and they're told to use these racks so the drips go down the hook shank. IMO, it would be better to fix the actual problem, instead of doing something like this and not fixing the cause of the drips, which is usually too much powder or the wrong temps for the powder!
I know some are using them for coating more, faster and that certainly makes sense, but I don't need that much production to use racks. I can coat & cure enough jigs in a day, just painting one at a time & hanging in my oven.