I used one for years, mostly as an an all in one tool with the blade just behind the applicator. I used it with a pole too, applicator facing one way and the blade the other. I found it was only really practical if I used it to do windows that were just too high to reach from the ground. soap the glass turn it over, wipe the blade, and pull it from top to bottom, wipe the blade again and repeat untill you clean the whole pane.
As an all in one tool it is a brilliant piece of kit, the jobs done in a single pass.
The only thing I have against the backflip is it's weight, that's why We switched to the Wagtail, it only weighs half as much. I think a dogeared Wagtail is the best bit of kit ever for trad cleaning. Like anything else it takes practice to get the technique right. We have been using them for over a year now and would never go back to using a seperate applicator and a sqeegie. Why go over the glass twice when you can do the lot in one go? The Wagtail may be seen as some as just another gimmick, But, they have been using them for years in Australia where they were invented. I believe that a new design is being brought out. I would be the first to buy one. Dai