Of course it's a good and new idea that will work on specific windows and customers. Lazy buggers need not take heed, but there is something in this for selected properties. Also as well as totally eliminating the spotting issues, such as busy main road jobs or extremely windy days, you could also work with a tds of a considerably higher ppm than just leaving glass to dry naturally.
This is not for every single job as James has already pointed out, but it does have merit in the right situations.