I recently purchased a Pioneer plasma. However, before purchasing it I was probably the most paranoid about screen burn on this forum. In the end I went for the plasma because screen sizes at around 60" are just not available in LCD (unless you want to pay crazy money). It is early days so I cannot say that the screen burns but what I can say is that the image quality is better than my previous LCD. I am still within the first 100-200 hours so I am being pretty careful but there have been instances where my wife has left a static screen for longer than what is advisable - to my relief there was no burn or image retention.
The longer I enjoy this TV, the less paranoid I am about screen burn so for the time being I am a very satified customer.