Two parter here guys.
First what is everyones take on a water filtration system such as this: http://www.autogeek.net/clinhofianda.html
I'm interested, I don't necessarily have the hardest water at home, but it is city water, that is not softened coming through my hose outside. And there is a tiny bit of sediment. The new house I'm looking at has well water (yet it's in the city, long story), and it's quite full of sediment, leave a glass sitting for a hour, and it will have a couple of millimeters of sediment and rust in the bottom.
Last night while out for New Years it rained, and froze to my car (as well as everyone elses). How does that affect water spotting when you warm up the car, and the hood gets warm, windows defrost, etc.