I love Zaino Z-1 and Z-2 and wondered if any of you have paid the $13 for the glass polish? Is it worth it? I use lemon juice and water which seems to be a good cleaner and super cheap. However, my new 2004 WRX seems to keep developing a film on the inside, esp. the rear window, which I want to prevent. I am a non-smoker so it isn't smoke.

Ideas or suggestions are appreciated.

Scott