i usually smoke out of a glass pipe, and never use a screen in it.. i did come with one of those glass screens, but they usually last about a day or so and i'd end up ashing them out of the car window, not to say that smoke and drive, don't know where you got that idea from...
anyhoos, yeah, no screen, takes about a day or so of smoking for it to get gunked up enough so that not having a screen doesn't really make a difference imo.. just gotta be careful on the first few session on a clean bowl, don't pull too hard or you may get some bud in your mouth..