Deep Eddy put a big shiny tank in front of their building for PR purposes during a prolonged drought in Austin. It worked so well that their competitors had to put in tanks to advertise that they used rain water as well.
They did find the softer water to be an asset to rinsing rugs, so the tank farm in back of the building was added. The filtration is simple and the system requires very little maintenance, with no algae build-ups or tank cleaning required.
If you live in a hard water area and have the room, installing rain water collection is worth thinking about.