I was wondering if that stuff was worth the money. Isn't it around 4 bucks per spray can?
Yeah, It's like 3.xx something. Kinda pricey but definitely better and so far it seems to last for a good while. I use a microfiber on the glass which doesn't seem to absorb as much like a cotton towel would so you're able to get more coverage. Also, use a towel that was not washed with any fabric softeners, it'll smear off on the glass making a light funky film.
RainX is some good stuff. Just don't apply it on or near a windshield chip. When you decide to get the chip fixed, the resin will have a hard time adhereing to it.
When cleaning glass it's best to do it at night with light shinging from the outside in, so that you can see the streaks. I use a foaming type cleaner (sprayaway) and newspaper, and never have streaks.