Glass is a neutral, non-reactive, near-impervious surface, so no matter what you use, the process of wet-cleaning consists only of dissolving the dirt, then removing the dirty solution. Streaks in cleaned glass come from only two places: gunk on the glass that didn't get cleaned up all the way to begin with (ineffective or incomplete cleaning), or from stuff in your cleaning solution that gets left on the glass (haze/film). The more complicated a glass cleaner, the more likely it will leave crud on your glass. Save yourself money and do a better cleaning job: A light solution of ammonia in water is the purest and usually most effective glass cleaner. It is also cheaper than any commercial product. To avoid streaks, just make sure you use a completely soft, clean, absorbent cloth, and wipe it up before it dries. If you wait too long to wipe off ANY cleaner, the evaporation will leave a residue that may well streak.

Windex is just ammonia solution with fragrance and dye. Why put dye on something you want to be clear?

Sometimes you have to use stronger stuff FIRST depending on what is on your glass. Tar/bugs/oily smoke on the outside may require a first cleaning with a bug-and-tar remover, Goo-Gone (a citrus cleaner), Goof-Off, etc. On the inside, esp. if there are smokers in the car, try a citrus cleaner. Denatured alcohol (NOT thinner) is an awesome cleaner for stubborn gunk. But in either case finish up with ammonia.

If you are getting streaks you may also have a dirty rag.

if you have driven through a lot of dust, or there has been construction or a lot of dust sireld up in your area -- like say your neighbor comes out and uses his leaf blower near your X-fire -- before using any cleaner, try using a duster to get dust off. All dust incl. household dust contains minute particles of extremely hard minerals including silicates. If you start cleaning without removing dust first, you are basically using sandpaper on the surface you are cleaning. Over time this results in fine "swirl" scratches, dulling paint, topcoat, chrome, plastic lenses, and potentially even glass.