We have hard water in my area so sometimes there is an issue of water spots rarely as the Simple Cherry rinses good off the glass.
The Simple cherry has rinse aids in the mix so it helps with the hard water spots.
Before I bid the job I mention that there could be hard water spots if they don't have a water softener on their water system so that they are aware it is a possibility. I do not professionally squeegee the windows unless they want to have the windows squeegee cleaned, this way they are aware of the possibilities and so far nobody wants to pay the difference and can deal with a few water spots if they happen.
We have hard water here but the simple cherry really rinses good off the windows but I only do 1/4 to 1/2 of he house at a time to help keep the mix from drying, that could help.