as said, your obviuosly using it wrong, i never have any complaints, had a handful in the beggining but not now
i spend time and do a good job, better than any trad cleaner
i put a post on here the other day, i had a old couple that i had bee doing for 3 months, but they were never in, the 4th time they were in and i saw the pole and how quick i was and came running out "your not our window cleaner, youve never finished, we want someone to polish them"...bla bla bla
anyway, the next month i missed them out, the old chap came out and couldnt apologise more and that he was wrong, then the lady also came out and couldnt apologise more...
speaks for itself really, use wfp properly and you WILL get good results, rush and dont use it propeerly and expect to get a crap job, as with anything