I think it's a great product that does everything it promises to do, if not more.
But I also have to somewhat agree with clnfrk's comments. There are just places in a car that you cannot get to without water and pressure. On some cars, I can spray a certain crevice or in between window moldings and mud literally pours out. Since I am a weekend warrior, maybe I don't have the same mentality as the average consumer paying a detailer to work on their car, but if I were to pay someone to clean my car, I would feel somewhat cheated if the car wasn't as clean as it could have been.
For example, if I did this professionally, I could see myself using ONR on a car I take care of on a weekly or bi-weekly basis if I got it completely clean to begin with and it hasn't been long since it had a regular wash. But if it was a brand new customer, I would feel like I was cheating the customer.
It's like taking a shower. You could wipe yourself down and feel "fresh" for a short period of time, but eventually you're going to have to take a real shower. And a real shower isn't just stepping into the water and lathering yourself up. You got areas you have to scrub (behind your ears, your neck, your back, etc.) if you want to be fully clean.