So I was curious how the water softner in NXT Car Wash works and I think I may have found an answer:Engineered water softener helps reduce deposits in hard water, leaving behind a spot-free finish.
My original assumption was that perhaps the NXT Car Wash is formulated to leave behind some chemicals on the paint that would retard the formation of water spots. I believe this is wrong.
From the article on howstuffworks.com, I believe the NXT car wash would only neutralize the water spot forming metals within the car wash bucket. So after you rinse the car wash off, then you'd still have to wipe off ASAP.
If you tend to wash and rinse your car a section/panel at a time, then I suppose the NXT doesn't offer too much of an advantage over other car washes. However, if you tend to wash the entire car then rinse, then it might provide some benefit in terms of preventing water spots from forming.
These have been my conclusions I have drawn from the limited information I have searched around for. Please correct me if my conclusions are misleading or false.