Once you accept 1st cleans will take a lot of time after that you,ll have got used to the technique and results are good. Gone upto about 35' so far but got a job in hand at just over 50.
I also use it on some office windows above workstations where I dont want to be climbing aver computer stations and trading. Very acceptable results.
Ps I made up my own with a pump, hose and fan jet as I didn't want to lash out loads of cash to fing the resuls were useless. Used Vikan easyshine head and pads, but also bought 2x microfibre floor shine heads and pads as the area of glass was large and glass hadn't been cleaned for years. Used them first then finished off with Vikan pads. Just realise it will take time.
Craig.