OK so I have one more minute to post here before I need to go to sleep so I'm not a zombie at work tomorrow...
Basically, I spent quite a bit of time with the 50PZ85U today, and quite a bit of time with the LN52A650. They did NOT have an LN52A550 on display today, but they did have an LN46A550, so I used it for comparison but did not give it as thorough of a look-over.
My thoughts now? The Panny 50PZ85U produces one hell of a uniform, gorgeous picture. It was one of their "Featured" tv's so they had it in its own area with some way-too-bright sounding klipsch speakers blasting into my ears as I watched some scenes from King Kong and from Chicken Little. The motion on that plasma is excellent, I noticed absolutely no motion blur whatsoever, and I thought the black level was superb. One thing that did bother me was that the screen showed a TON of glare in the darker scenes, although granted I was in a giant big box store and I could see reflections of an entire wall of LCD tv's hanging up in the background behind it. However, even with this much light, I could barely see any reflection at all during the "bright" scenes in the movie, and since my setup is going to be in a completely light controlled room (one sliding glass door and one window, but both will have full thickness curtains/shades and there is a deck outside above these windows, so glare is not a problem). I was impressed with the plasma.
And now onto the LCD tv I spent the most time with, the Samsung LN52A650...obviously seems to be considered by most people to be one of the best (if not the best) LCD for under $2k. My thoughts? When looking for it, I could see some motion blur, but it was hard to tell how much of the motion blur was from the TV itself, and how much was just from the CGI in the demo they had playing on all of their TVs at once. Reason I say this is, this LCD was directly next to a 50" Panny plasma (the 50-650 series plasma), and I could see the same motion blur on the words as they flew by in 3D animation. The source was definitely high definition, but I think the CGI job in actually creating the video was very poorly done. Not helpful to me, because it left me with nothing to compare it to. I need to see if they can somehow just run a blu-ray to the TV for me so I can see what it looks like with a direct, high quality source. I don't anticipate that the motion will end up being too too bad for me. And yes, I did my viewing with AMP turned completely off. I did notice that the contrast on the 650 series was noticably better than on the 46 inch 550 I saw just a few TVs away. Although, the black level honestly wasn't too terrible on either of them, the mid-range Sony LCD perched between the two of them looked completely gray in comparison.
Anyways, I'll post some more thoughts tomorrow, but let me know what you guys think.