I have yet to spot any dead pixels on my 20 inch Dell. I also can't see any on the two 23 inch Apple Cinema displays I have had in the house recently.

I haven't run any special apps to find any though, if I can't see them normally I don't want to know about them...

My only complaint about my Dell is that the stand sticks out too far to the front, meaning I can't get my keyboard as close to it as I would like. The Apple displays have a similar problem, but at least in that case the stand is very thin, allowing some keyboards to overlap it.