Have had my PWD8 for about 3 weeks now, and have noticed no retention issues at all. My set probably gets abused more than most will, as the kids will insist on pausing SKY+ and leaving the image on the screen for fairly long periods, and still no problems. This was one of the reasons for chosing the PWD8 based on the recommendations of people like HorneyDragon and MAW (cheers guys), as no matter how much I look after a screen, my family will continue to use (abuse)it just like our old CRT.
I have wound back all the settings for running in and taken it out of dynamic mode.
Still over the moon with the panel. The styling (or lack of it) is beautifully minimal with none of the bling of some of the other screens available. PQ is fantastic and will only get better when I start fiddling with HD, component etc
Martin