I have one and use it all the time. Honestly its not a revolutionary product as you should always deep clean your pads after every few cars using something like dawn power dissolver but I do think the GG PW is excellent for quick pad cleaning during polishing. I often find I will use the same 1 or 2 pads for an entire car because I just keep re-washing them in the GG after 2 or 3 panels of polishing. I dont buy as many pads as I used too simply because I have this unit.
It seems pricey at first but if your saving time on details and $$ on pads eventually it will pay for itself. Also if you have pads which are difficult to center than this is a must, that way you do not have to keep pulling off and re-applying your pads to the backing plate.