Well, I finally got around to using this thing. I will say that there are NO spots on the Viper now, not even on the glass! On the other hand, I'll second the opinion that using the Mr. Clean soap didn't seem to get the car as clean as other methods. As a matter of fact, the brand new sponge I was using with the soap turned VERY black. Much blacker than it should have been given the amount of dirt on my already fairly clean car. What I think is happening is that there's somthing in this soap that reacts with dirt or perhaps pollen, (which my car was covered with) turning it black. It's that bad. Some spots (areas where bugs had hit) seemed to absorb this black color and then had to be scrubbed even harder to completely remove them. I also noticed that this soap seemed to react to the brake dust on my wheels and turned it into a gooey paste-like substance which was hard to remove.
Overall though, I'd say it's a good product. I'm still amazed that there are no spots anywhere on the car. With this highly treated water we have here in Northern Virginia, water spots were always a problem with my car, even when using towels to dry it.
So, I think the best method may be to use the regular Zaino soap in a bucket and use the filter piece of the Mr. Clean system for rinsing as it really does eliminate the need to dry the car, hence lessening the chance of getting swirl marks. That's worth the price, in my opinion.
Oh, and for whoever said it took forever to rinse the car with the filtered water, I didn't find that to be the case. Just make sure you're rinsing the soap off with the regular water FIRST. The filtered water is then used to rinse off the non-filtered water, not soap.
--Rob