So now that I have had my pn64d8000 for a day or so I can say that it is absolutely amazing!
We replaced a 10 year old CRT RPTV that lost it's convergence I/C, but we have a Samsung plasma in the bedroom. When I watched the C550, I thought to myself that it couldn't look THAT much better, maybe the D550 would be just as good, but it certainly does make a huge difference. Star Wars looks night and day different between the 2 panels, not just the deeper black levels, but the overall color gammut and clarity.
Then in addition, this is our first 3d tv, we watched and oogled at a few trailers and those 3D IMAX movies that are free on PPV and we spent several hours playing Uncharted 3 in 3D. I especially love how REAL the water looks in 3D! I have only noticed some rare crosstalk where it seemed like a goof in the source material, less frequent than what I've experienced in the 3D movies in theme parks and theater releases.
I heard some slight buzz initially, it sounded like a wasp, because it was a wasp! No more buzz!!
I occasionally see brightness pops, but I understand there is a FW fix for that.
I am in no hurry to install it. It doesn't bother me much and no one else in my household has even noticed it.
If you find a good deal on the D8000, jump on it!!! I highly recommend it!