Up until recently, most of the 4/3 SD feeds I've watched have had the right/left sides cut off, so something is always missing. Notice it mainly on football games, where you can't see the DBs in SD.
I almost never watch FOX, except for two or 3 times a year when the team I watch is on FOX, but I've noticed that this year FOX is putting the NFL games in letterbox. If I have my TV in regular 4/3 mode, the viewing area is pretty small, but the good thing is that letterbox in 4/3 can be zoomed up to fill the whole 16/9 screen without making everyone look wide, or missing stuff at top/bottom. Not nearly as good as HD obviously, but I like it better than watching a 4/3 game where they've clipped off the edges so you can't see the DBs.