I purchased the 40xbr2 the wednesday before thanksgiving. I'd been doing alot of research before hand, and had read a large amount of this thread prior to purchase. I realized that the clouding could be part of the territory, but I've had very good luck with Trinitron's over the years and decided long ago my next tv would be an xbr.
Bingo, within the first minute of turning the unit on, I noticed the clouding. It was a concern, but at that time I wanted to see what else the tv had to offer.
After browsing my HD channels for a while, I noticed the screen being much too bright in low/no light conditions. I wasn't going to mess with the picture controls until I could run video essentials on it.
What I did do was to turn the light sensor on.
I used the lumisponder/light sensor on my last set, so I guess I've grown used to it. The light sensor does a fantastic job, in my opinion. The clouding effect on my set on an open input, while still somewhat noticible ---if you look for it--- decreases by what I would guess to be around 70%. The picture while viewing content is still ever so brilliant, but not overbearing like watching the vivid mode in a dark room. I have not been able to notice any clouding while watching shows/dvds with the light sensor on.
I've yet to use Petmick's calibration info, but will shortly. I had run video essentials on it, and brought the backlight, brightness and picture all down. Color was pretty spot on, with only changing to a r2 on hue.
My set is a serial 8032xxx with an October 06 build date.