I'd echo Lee and Chuck: be extremely careful with Simple Green-- when you use it don't answer the phone or get distracted because damage will occur-- in a while it is no longer just microscopic either, but you'll notice with the unaided eye results just like Chuck describes. I also had poor surface results from Blue Lightning Parts Wash/Carb Cleaner, another water soluble and biodegradable product.
I would not hesitate to recommend many of the items from Griot's Garage, as I think their products do as they describe and quite well, too.
Ken Wehrenberg, Hermann, MO