I have used rainX for years. In the past 1-2 years, I have been using zaino glass polish and then every time I wax the car with Z2 or Z5, I throw a coat on the windows. It works great, and really adds to the detailed look of the car. Also, it makes window cleaning a breeze. They come out perfect after washing with just a little Z6 QD'er. I don't use any glass cleaners except for the insides to remove plasticizing film that accumulates from the interior materials.
A few weeks ago, I put rainx back on my front windshield for a comparison. I like the z2 on the sides and back too much to put anything else on them.
Anyhow, RainX works great for me. I have no streaking or wiper chatter and it really helps with the rain. I think most of you are not prepping the window properly before apply RAINX, and that is leading towards your negative experiences.
I start off with a glass polish. Then I clean the windsheild off with my home made mixture of vinegar, IPA, and water. RAINX goes on easy, I apply it thick and rub it on well. When it hazes after a few minutes, I put another coat on, pretty thick. I wait 10-15 mintues and buff away. It all comes off, but a film remains and smears and streaks. If you go over it with a damp towel it comes off very easily, and does not come back. It might take some elbow grease but you can get it all off and then you are set! I have found the RAINX effect lasts more than a month. For the record, on my BMW, the windows sheet water beads away with nothing on the windows so rainx just helps that much more. I think it is a factory coating of some sorts.........
Hope this helps.......