I feel I have to stand up for Sony here (and before you say it, I'm not a massive Sony fan or anything - I have usually stayed away from Sony because I always felt you were paying a premium for the name).
From reading this thread, I've found myself getting increasingly paranoid about my 40W4500 being affected with this clouding problem, and I keep finding myself sitting looking at any blacks on the screen for evidence of clouding, rather than just enjoying the actual programme.
Then last night I sat down in a completely dark room, changed by V+ box to a radio channel (to give a completely black screen), and sat there trying to find evidence of this clouding. Even looking specifically for it, I couldn't see any. Perhaps at certain unnatural viewing angles, I might see some backlight bleeding in the corners, but nothing like the pictures being posted here. I have found my tv to be absolutely stunning in every respect, and I think WHF's review was spot on. Obviously I'm not trying to say that other people's problems aren't there (because the pictures speak for themselves) but I don't think every TV can be affected by this (or at least, not every 40" TV), because mine's definitely not. However, I do have the backlight set to 0, and I have the light sensor on, but even turning the backlight up didn't have any real effect on the blank screen. And the TV had been on non stop for about 4 hours when I tested it.
As I said though, clearly some people's screens are affected by bad clouding, but not everyone's, so people might think it a risk to buy this TV, but I would say, don't totally discount it on the basis of this - if you get a good one, it is a great TV.
(I will test it tonight with the light sensor off etc, and see if it makes a difference).
Sony KDL-40W4500; Sony BDP-S350; Onkyo TX-SR606; Jamo 102HCS5; Virginmedia V+; Apple TV; Nintento Wii