Totally agree. Invisible Glass is good stuff.
Here is what I do. I use glass cleaner and a good microfiber cloth to get as much dirt off as possible. Then I use a clay bar. Your glass gets just as many contaminants on it as your paint does. If any of you guys have never used a clay bar, go buy one. You need a lubricant for it you will use a detail spray. Maguires and mothers both sell a Clay bar kit that includes a clay bar and a 16 ounce bottle of spray detailer.