I finally found some time today to clay the car. It really is amazing how much crud can be sticking to the paint of a car that looks clean. The spray detailer liquid on the paint turned practically black and the microfiber cloth got really grungy. I'm not done. I only did the hood, front fenders and doors today. I'll finish up tomorrow and put on a coat of wax.
It does what it says, though. The surface was remarkably smooth after the clay job.
I did drop a piece on the ground

Tossed it.
I'd say it's worth the dough. I think it was about $20.