If I watch hockey on an SD channel vs. the HD equivalent channel it isn't a different recording, but it is very clearly worse than HD. The graphics in particular are fuzzier and it can be hard to read the clock/score vs. on the HD channel. The graphics are certainly be optimized for HD now; and maybe we would just have bigger overlays in the past to reflect the poor resolution (but with smaller screens, maybe not). Also, a CRT has a different amount of "fuzz" to it than a new LCD TV; so some details which look ugly now might not have mattered as much.