It's time to get rid of my Sony Wega 40-inch TV, which cost over $3000 when I bought it years ago. My local A/V retailer carries Sony, Samsung, LG, and Sharp, and a local furniture store offers Panasonic, Toshiba, and Hitachi. The most important features to me are sports, movies, and Ethernet (I have a lot of movies on my new Windows 7 PC).
Most of the brands you mention are fine, though I wouldn't get a Hitachi, since that company seems to be falling far behind in the TV game. I see only two UltraVision LED models and four CCFL models on its website, all of which are about a year old. My current favorite brands are LG, Panasonic, Samsung, and Sony.
Virtually all modern flat panels have Ethernet connectivity for access to Internet and local-network content. Just make sure that the one you get has DLNA capability, which will let you access the movies on your PC.
All the companies you mention make LED-illuminated LCD flat panels (which I recommend over CCFL-illuminated models), and LG, Panasonic, and Samsung also make plasmas. Which should you get? If you often watch during the day and don't have good control of ambient light in the room, an LCD is the way to go, but if you can control ambient light fairly well, I prefer plasma for its lack of motion blur, wider viewing angle, and generally better black levels.
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