Yeah I'm actually in the same boat. I've had a Samsung HLP-4674 for over 4 years and made the jump into LCD back in November. I got the LN40A500 and was not impressed at all. All kinds of uniformity issues and bad flashlighting, washed out colors and horrible viewing angles. That's when I learned about the Samsung panel codes (A,C,S) though it seems now you can't really justify quality based on the panel code alone, though it appears S is the best, while A,C are lower quality. I myself got a C panel. I sent the TV back and so far I've just been using my DLP, but I've been researching a lot about LCDs this time around, and after finally going over to Best Buy and Costsco the other night, I saw all the sets I have been looking at, and here's my take....
I had narrowed it down to the Samsung's (550, 630, 750) Sharp LC46D65U, and Vizio 470XVT.
The Vizio and Sharp were both $999 and the 550 was only $100 more, but then I started reading about the whole 120Hz and Blu-ray and they have to go together, so I threw the 630 in which was $250 more than the first 2 sets. I was then recommended to spend the extra $$$ to go from the 630 to the 750 for only $100 more than the 630, so all of a sudden I went from $999 to $1450.
I used to work at Best Buy, so when I was there my friends let me tweak the tv settings to my hearts content, so i set all 3 Samsungs to the exact same settings, and luckily they were all right next to each other. The 750 did look a little better than the others, but not by much, the colors were a little more rich and blacks were darker, but it certainly didn't blow the other 2 sets out of the water, like I thought it would. So then I compared the 120Hz to the 60Hz, I could see a little difference, but again, it wasn't anything drastic as I thought it was going to be, so I decided the 550 would be the set I would go with.
Next I headed over to the Sharp, and compared that with the Samsung. The picture seemed sharper on the Samsung, and the colors more vivid, so the Sharp was out.
Then I drove over to Costco and checked out the Vizio. There was no Samsung TV to compare it to there though they did have Sharps, Sonys, and Toshibas, and the Vizio looked terrible compared to the other sets.
So my decision is to go with the LN46A550, I just have to sell my DLP first before I can get my new TV, though I'm debating whether I should wait, since the price on the 550 is the lowest I've ever seen right now.
Hope that helps in your decision.
**This is interesting, I just checked Amazon, and the list price of the 550 just dropped $100, it was listed at $1599 and they were selling it for $1099, now the list price is $1499, and they are still selling it for $1097, makes me wonder if they're gonna drop it down to $999 or even lower....might have to wait this one out**