The more expensive Widescreens, e.g. the top of the range Sonys etc do a much nicer job of "stretching" standard broadcasts to widescreen. I'm not 100% sure what goes on but I think they use software to apply the stretching to different parts of the screen so you don't just end up with noticable distortion.
It's often better to leave the TV in switching mode so when it's receiving widescreen it'll fill the screen and when it's normal broadcast it will remain square.
