Hi, I viewed the 40W4000 about 6 months ago and found that the amount of digital artifacts / noise was just not acceptable for me (sitting approx 9 ft from the screen). Since then I have viewed the 40W4500 (better but still not great) and the 40Z4500. To be honest it was only the Z4500 that I found "acceptable" and would actually want to watch in my lounge. Don't get me wrong, it's still not perfect, but IMO what I would class as "acceptable." Saying this though, everyone has a different perspective on "acceptable" so you might find the W4000 to be perfectly OK for you. I would try and track one down in a Sony centre for a viewing as they tend to use reasonable quality signal feeds so gives you a good idea of the pic quality in your lounge (as opposed to the currys / comet brigade that I've found use a rubbish SD signal so make the TV's looks worse than the are in reality).
Hope this helps,
Sam