Well, I might as well throw my hat into the ring . . . . I'm an audio/video engineer living in Norway and our Sony sets are sourced from Slovakia, if that makes any difference. I spent literally hours examining and testing the 40W4500, the 52, 55 and even the 70 inch versions in this series. Every set was stunning and passed every signal test I threw at them. The 70" model was particularly spectacular even running SD sources, although the garbage in - garbage out rule still applies here.
The only anomoly I noticed on the KDL-52W4500, which I went for in the end, was a series of black bands slowly moving vertically up the screen, when all inputs were wired up, however I traced this down to a fully wired scart cable connected to a Pioneer DVD recorder that was causing the interference.
Making a custom cable using only the required signal wires cured the problem.
I remember a few cases many years ago, when our Sony CRT sets came from a factory in Wales rather than Japan, and at that time they did have a QC problem with the UK sets and indeed had to modify the design to take into account the fluctuation in quality of some of the locally sourced parts. I guess the simplest solution here is to try and buy from a reputable dealer who will let you audition the equipment using your own reference disc that you can bring to the shop. Dealers like this may charge a few pounds more than the box-shifters but how much for peace of mind? As a footnote, any electrical item purchased in any shop here in Norway, be it mail order or local, can be returned for a full refund during the first thirty days.
Any manufacturer that ships in volumes can have some rogue sets in the wild, but at least here in Scandinavia, we haven't seen any of this clouding effect that everyone is talking about and believe me, I've been looking.