My original 17" CRT was huge and not only took up most of the desktop it only gave me an actual screen size of 15.5"
Since changing to 19" LCDs it enables me to have 3 monitors (panoramic style) on the same desktop ( one setup is for a dual monitor setup of one PC and the third is for a second PC which in the past always had to be situated elsewhere because of lack of space, even though I have a large corner unit desk.
But the main benefit I find is being able to have them much further away from my face, thus saving eye strain due to the flicker that we can't actually see.
As for widescreen monitors, well unless you are watching widescreen movies or doing spread sheets, I don't really see any benefit in them, lets face it, most of the work we do especially for typing letters etc is on A4 size paper in portrait view.