Spot-X Glass Restorer Reviews?

My husband has a 30 year old truck that he just could not get the hard water spots off of the glass...he literally had tried everything with no luck. He tried Spot-X and the glass looks brand new. You have to follow directions exactly and will need to put some muscle into it, but this stuff really does work (I was skeptical when he got it, but am a believer now!) You may have to do more than one application...just have patience.