what is the point of using antialias? for what purpose would someone want that effect?
Anti-aliasing removes "jaggies" aka artifacts from pixels. The hard edged pixels makes the pixels much more visible and can easily kill the mood of a game (especially on a low-resolution monitor). Also on thin geometry (line a car antenna), lack of anti-aliasing can leave very visible line artifacts (the line of the antenna would be broken into several lines with gaps in between). Play half life 2 without anti-aliasing and then with, and you'll see why the 'effect' is purposeful.