Using a QD spray is better than no spray at all. It's just as dangerous to the paint as washing is. Let's face it, no one is absolutely perfect when washing their car. Both washing and using a QD spray has the chance of leaving some light marring on the paint.
The QD acts the same as a lube and lifts dirt. It's better than nothing, and perfectly acceptable as an in-between wash type thing.
'11 BMW E92 ///M3 - ZCP and DCT
'13 Toyota Tundra - 4x4 Platinum CrewMax, 5.7l iForce V8