So, I'd consider my experience with this TV in the last 3 weeks to have been 'good' or 'so-so', but yesterday I got my PS3 from amazon after finally deciding to pull the trigger on bluray. It was a bluray playing on the samsung that originally convinced me to go this route.
After making all the connections (and finding out my onkyo HTIB didn't actually support HDMI audio, just passthrough) I decided on planet earth as my first bluray to watch. Now, I'd never seen this program, and only got it because I'd seen it mentioned in passing on this forum.
I was amazed at the picture, it's truely amazing. Real life is the only comparison I can make, maybe not that good, but the picture actually seemed to have depth, it was amazing. The scenery and shots were unreal at times, most shots seemed to have the quality of a moving fullscreen photograph. Crisp, sharp, clear, and deep.
Now are the blacks bezel black? Hell no, but all I've done is try messing around with contrast/brightness, dynamic contrast, black adjust, and gamma. Going to have it ISFd at some point in the next 3-6 months. I found a decent medium where the blacks were as black as I could get them, without making subtle scenery (like shadows) disappear (is this black crush?).
Anyways, I'm sure there's a bunch more that can be done to perfect the image, but what I saw was quite stunning. Blu-ray is definately amazing, haven't watched HD-DVD yet, but I can't imagine there's a HUGE difference between them, not saying there isn't one, just not a massive one.
A big tell-tale sign to me, was that after watching a few episodes of planet earth, my wife said the TV was worth the money, which I don't take lightly, she didn't see the point of spending nearly twice as much as an older model 50" PDP.
I'd say for content other than BD/HD-DVD (not sure on games), these 1080P TVs aren't really going to shine over older models that much, especially not at just 50".
Only problem is that there's a huge pricejump from an older 58"-65" 720P PDP, and a 58"-65" 1080P PDP, and that's where the large gains are really seen by the average person, keyword here 'average person'.
Either way, blu-ray on the 5084 looks amazing.