Another pioneer vs panasonic thread

Thought i'd finally decided on the 50" panny - but, although its meant to be available in Shanghai where I live, no sign of them.

Now the Pioneer 504 has turned up. I'd gone off these because of poor blacks and more danger of screen burn, but don't know if I can wait for the Panny.

Those who have had the 504 for a few months now - happy with the choice or do the blacks or any other things bug you?