I do a close with 5 houses and I clean 4 out of the five. One of them
HATES wfp. Her windows are upvc, as are her doors and they come up spotless every time.
She even said to me "You're the best window cleaner I've ever had but I hate that brush thing!" :

Anyway - she's been a custy for five years now and yesterday she saw me with my gate ladder going into her neighbours and she came out looking all hopeful and said: "Ooooh are you using ladders now?"
"No" says I "I just use it to open (your neighbour's) gate when she's not home."
She literally stamped her foot and said "Oh, I was hoping you'd gone back to doing it the proper way!"
I grinned and asked her why on earth I would do that when if I did I could fall off and/or leave her frames less than gleaming and her glass not so shiny.
She gestured like a poof shutting an up and over garage door and said "I know, I know! I just hate that thing!" pointing to my wfp.
Her hubby just stood behind her rolling his eyes and grinned.
Gotta laff!