I've had these nasty Acid rain/hard water spots on my glass and used Zaino glass polish to remove them. Very easy to rub on and off with miraculous results, see for yourself! I recommend this if you have the same issue I had.
I didn't. I did try a cleaner wax when I first noticed them. I got them to fade only a little, to what you see in the before pic. I'm a long time Zaino user and decided to give their glass polish a shot since I have mostly all their other products.
Btw, all of my windows were spotted like a cheetah. It looked really nasty when everything else is clean. I was glad to be done with them and honestly would have been pleased with any product that would've produced my results as easy as this was.