My ONR (Optimum No-Rinse) arrived last week, so on a very cold day I decided to give it a try.
I used my battery power washer to attack the lower side panels and rear hatch, then doing one side at a time I sprayed the ONR on to the car, and despite the name, rinsed it off with the power washer (using the bottle attachment, a 2-litre mineral water bottle is enough to thoroughly clean one side of the car).
Most of the dirt remaining after the initial wash came off with the power-washer rinse, and what was left was easily wiped away using a microfibre cloth. I'm reluctant to believe the claims made for ONR, believing that if you wipe dirt away using a cloth, you're still dragging a dirt-encrusted cloth over your paintwork, but even so, the results were acceptable.
I might try it a few more times over the winter, then have a good look at the paint and check for swirls under a powerful torch. The worst-case scenario is that I may have to break out my DA polisher when the weather improves.
As a means to give your car a quick, and apparently effective clean during the winter months, or a hosepipe ban, this might have something going for it. I'll report back at some point, and let you know if there's any paint damage.