When the set upconverts SD it has to "fill in the blanks", essentially "make up" pixels to put into the extra scan lines. This issue is very important (IMHO) but is not officially addressed by anyone as far as I know. I think CR does have a column for "SD picture quality" but I am not sure. Sales people have no clue about it since they make their money hyping the other end rather than addressing the reality that half of what you will watch is SD. I had a Sony Bravia and I thought it did an amazing job of this, better even then the broadcasters. For example, when I would watch the Simpsons broadcast in SD and upconverted by my set it looked good. When I watched an SD rerun of the Simpsons broadcast in HD and upconverted by the station, it had strange patterns at all the edges of everything, around everone's heads for example. The only way to compare is to get the store to switch on some SD so you can see how the sets handle it, but they either don't know how to do this or won't. My local Video Only store did switch some on for a while for me.

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra