I am a professional cleaner and this is the best product i have personaly used for this application
I have had a professional cleaning business for a number of years and this is the best product i have found and it is not awful nasty to use or harsh.  It delivers nice looking glass, an improvement to buildup, and i suspect it gets better with continued use and/or prevents further build up or at least alleviates it.  Nothing can perform miracles, and i think glass gets etched by heavy minerals over time, but this also sort of shines even that dulling for an overall improved appearance .  A little goes a long way so the price is worth it.  Good product.  I sought this out to purchase online after using it at a clients house and amazon had the best price and most convenience.
Rating: 5 stars