I always use QDs on my glass. I like my cleaning solution to be a bit more lubricated than plain water (glass is harder than paint, but it is still possible to scratch it), and since I use a sealant on the glass, I want something gentler on the LSP than most window cleaners (which usually contain varying levels of isopropyl alcohol). You do have to choose the QD though - some QDs can streak more than others, and while this is not as noticeable on paint, it can be very obvious when seen through your windshield.