Direct Quote for the lazy.
"Sorry for the long wait. We do have a fix in place. Dell has a firmware update that adjusts the ACC (Adaptive Color and Contrast) & ACM (Active Color Management) features, eliminating the banding issue when using the Desktop mode. All of these monitors have three display modes: Desktop, Multimedia and Gaming. The firmware turns off Faroudja video processing in Desktop mode. It remains enabled in the other two modes. Essentially, the updated firmware allows users to choose whether they want the Faroudja video processing feature on or off. I understand your time is valuable. I will private message all of you with details in the next day or two. Please update your forum profile."
I know Faroudja is a type of video processing to improve quality, it's used in a lot of plasmas, projection TVs and DVD players. Don't know a lot about the details, but it seems to me that the banding was also bad if not worse in Gaming and Multimedia modes, and apparently this "fix" only applies to Desktop mode, so I fail to see how it can address the banding issues entirely. Time will tell.