I recently purchased a 50" plasma monitor as a replacement for a year-old DLP. I was shocked to find that the set had such unstable black levels that I thought it was defective and exchanged it for another example (with, of course, the same result!).
In reading Audioholics' TV reviews I haven't seen any discussion of black level stability--does that mean that no problem was noted? Do you test for DC restoration?
Cnet seems to be the only on-line review site that specifically discusses this area of performance. I find floating black levels to be much more distracting than false contour effects.