As a panny 6 owner, i would of course say that it is best.
I think that saying most dealers are a little dissappointed by the panny 6 and think it is not as good as the 4 series is rubbish, just an excuse for not purchasing it (RossC, not a dig mate, i am sure the NEC is excellent but is a comment i hear lots of people say, NONE OF WHICH being dealers)......check out the threads on this forum, plenty of very respectable dealers think the PW6 is excellent.
I find colours, blacks, tones, movement and lip sync all to be superb and am totally blown away with it.
But, i would say that so many of the plasma's are now very good, like the fuji's, NEC, pioneer etc whichever you decide on ultimately you will be incredibly happy with.....just spend a while looking around to make your own mind up as different people are susceptible to different issues and will have compleetly different tastes in what a good picture should look like.