How good are HDTV's with non-HD signals?

I’ve looked for SD TV’s and most of the inexpensive ones are pretty bad. If I’m going to spend more for a good one, then I’d rather go to HD in anticipation of the inevitable future HDization of my house.

We have Comcast digital, I think the signal should be pretty good. I’m very encouraged by the large majority of your posts which report good results, I think I’m going to see if I can find a good set over the weekend.

Thanks again for everyone’s help!