The product works as advertized and works under the theory of proiding a very lubricated surface so the dirt doesn't scratch as you remove it. It's great in that you aren't using drinking water to wash your car.
There is a pretty good alternative if you wash your own car. Use a bucket and put a good car cleaner in it like the one Maguires makes. Very lightly spray your car to get it wet...do NOT do the hose a long time to knock off the dirt thing. Unless you've just come back from a mud trip off road of course....;^)
Use a sheepskin or substitute type mit and wash the car slowly. The car wash material you can buy simulates the highly lubricated surface to avoid scratching. It's far, far more effective than regular soap in that respect.
Try to wash very early in the morning, or later afternoon on hot days so the water and soap don't dry on your car. Lightly rinse with low pressure to save water, and don't worry about getting every single soap bubble off. The material is the high lube stuff and won't leave soap film when you wipe it off.
Using this method could likely use 50% less water for most people. The way I do it probably uses less than 25% of what I originally did. The key is in the material used for cleaning. Regular soap suds up way too much, and requires way too much water to rinse. Worse it doesn't clean nearly as well, and is more prone to allow hairline scratches be put into the paint while taking the dirt off.