It is getting harder and harder to find 4:3 monitors, so for me it's not my first choice that i now have a 1920x1080 as main screen. (I start drooling thinking of a 1920x1440 screen)
I actually got a 4:3 monitor on purpose though, since at the time, big widescreen monitors were too expensive and I wasn't willing to settle for fewer vertical pixels (for programming, height is more important than width for me) and I didn't want the hassle of flipping a widescreen monitor sideways.