Erm Sais Zak and I and about 3 or 4 other people so far on this post, jeez only posted my findings of 25 years in the car trade, a father with 40 years in the car trade and many other peoples experience as shown above.
Having cleaned hundreds of cars I've tried loads of different products for cleaning, polishing etc and quite often an old cheap method will be the most cost effective efficient way. My valeter uses Zak's method for interior windows aswell and he cleans thousands of cars/vans etc a year. He uses chemicals for some other car parts and good old water and cloth for others.
Just because you like to spend money on chemical methods is fine, that's what you prefer and that's your opinion. Personally I think your wasting your money on interior glass cleaner but then I'm entitled to an opinion aswell. If we were talking about exterior applications then that's a whole different matter and one where the application of a chemical product can help the water just run off the screen.
Not only that but the use of an old newpaper is probably up there as the most environmentally friendly option by re-using a waste product
and a cloth and water is pretty non damaging too.