Nick
We have a new 52W5500 that Ihave been singing the praises of since it arrived, and in my view the picture is getting better and better from "running in" and some suitable tweaks, Sky HD transmissions are fabulous, especially EuroSport and Rush HD, with the BBC HD about third.
I have not noticed any backlight issues to date, so much so that each night for the last four nights I have turned all lights off in the lounge and switched off the Sky box, so now there should just be power to the screen in a natural state, then to satisfy curiosity I check over the screen from my viewing position head on, standing up and from the sides and whilst I can discern the slightest imperfection of consistency across the screen (seems reasonable with LCD, CCFL lighting) I cannot see "clouding" or "bleeding" light.
I also have a 40X2000 which does suffer from clouding in the bottom left area of the screen, but nothing on the 52W5500
Don't know whether this helps or not??
Sony 52W5500, Yamaha RXV 2700, Sky+ HD, Chord ProDac interconnects,Chord HDMI, Denon 2930 DVD, Tacima 929 mains block,Chord Carnival speaker cables, KEF Q7 fronts, iQ6C, and Q2DS rears, REL Storm III and Chord Power Chords