I bought one and tried it on my wife's car. I didn't like it. It is too difficult to keep the area well lubricated while you are claying. In the past I have always held the clay in my right hand and a spraybottle of lubricant in my left hand, lubricating the paint as I went along. When I completed a section I would stop and wipe off the excess lubricant. When I tried the clay applicator pad, I kept grinding the clay into the paint because I couldn't keep the surface well lubricated. Also I feel that it is important to feel the surface as the clay slides over the paint.
I've used it also with meg's overspray clay and soap and water lube. I couldn't get the clay to stay on the pad. I think the soap and water got the bar too lubed up.
I'm not ready to give up on it yet though because while it stayed on the pad it worked well. I'm going to try different lube and clay.
I saw that advertised in GG's book and was concerned about having a bit of dirt get in the clay and cause scratches before you would notice with the surface being wet.
Claying doesn't take that long and I think the control of doing it by hand is a benefit.
I haven't tried it but here is my opinion on the matter. Claying is relatively quick but you also have to constantly check the clay and fold it for any particles that get into it. The last thing you want to do is oscillate that thing with a particle in it and cause some bad marring. To me it just seems to over complicate the process and potentially make it more hazardous to the finish.
I use it everytime on the flat sufraces.....hood, roof, etc...I spary the pad down with a QD. I have never had a problem and actually with the pad lubed I can do more area in a faster time. Also I have done it side by side, hand and pad, and doing the baggie test, I get a noticable difference. Just my opinion.