Not so good
Having loved their product that works on fiberglass, I couldn't wait to try this on my glass shower door.  It might have taken off some of the water stains, but I couldn't tell the difference.  It took me a long time to find something that would actually work on the fiberglass; looks like I still have some searching to do for the glass shower door.  Maybe I just have exceptionally hard water.
Rating: 2 stars