Schlieren free but is something else. You have the disc moisten well and pull the window sucker at a certain angle. This works well with practice. There are a few points which I then nevertheless nachpoliere with the cloth.
We also have a glass shower enclosure. This reflects the strength of the window sucker. Simply peel off the glass of several panels and finished without the shower is wet again.
When it comes to longevity, I have my doubts. The squeegee is indeed screwed but there is not a spare part for it. The opening to empty is a bit small, the rubber plug can come off and is hopefully available. The Akkulaugzeit is sufficient. All windows are clean, the shower wall withdrawn several times and the battery is not yet empty.
For normal window I would prefer a simple puller the window because of the suction speed. For hard to reach windows as in the stairwell or conservatory of Leifheit's
but recommended, also because of the short rod against the bar of our Leifheit floor mop has to be replaced, and then each window can be achieved.