Meguiar's Glass Cleaner Concentrate (D120) gets my vote.
I used to use Stoner's IG, until I was enlightened. Meg's Glass Cleaner at a 10:1 ratio can't be beat... not only is it extremely cost effective, but it also delivers unsurpassed performance (IMHO.) Streak free everytime is what I look for, and this stuff has yet to dissapoint.
Erik's tips on improving your results with this product:
Dilute 10:1 with purified water ( recommendation only, not a necessity.)
Use a high quality nappy 100% cotton terry towel, or even better surgical quality lintless cotton towels. I prefer this method of application instead of a microfiber towel. Some MF's leave small towel fibers behind on the glass which is usually only seen under certain lighting.
Meg's D120 is a great product, it's so great I even got my mom using it (she said bye bye W****X.):cheers: