I do whack on all the heated options when in the car; windscreen, back, side mirrors and seats. But the windscreen takes some time with heavy frost. Used to use a de-icer spray, but let's just say that I punctured the can once and looked like a dick. Bought a plastic ice scraper from Halfords which was ok but by the time your done you have frostbite yes I know ice is cold. Probably doesn't help that I give myself about 20 minutes to rush to work. I'm thinking speed and efficiency....blowtorch...boom
I keep a spray bottle filled with one-third water and two-thirds 90% isopropyl alcohol in my car. Spray the windows with this mixture and then scrape with a regular ice scraper. Works like a charm here in Canada.