water fed poles

you know, some window washers swear by these things but it just doesn't seem right. You take a long pole and attach a scrubber at the end of it. You feed it with some purified water and scrub the glass. IT is supposed to not leave anything behind but I just don't see that happening. For one, the WFP system is costly so you better have plenty of places to use it on before you go out and invest in something that cost this much. I will have to seem some really, really, really good results before I break down and buy a wfp.