The Samsung E7000 series is excellent. I actually had a D7000 64" plasma from them and I am very satisfied with the model. The heat that it gives off is there, but really isn't something I've ever noticed unless I'm standing a foot away from it. In the Winter it helps to keep things warm, but in the summer it costs me a bit more to cool the house... So, I guess it balances out.
For long term reliability, I think the Panasonic ST series is better than Samsung, but I think for the image quality, the E7000 may be a bit better than the Panny.
I have no real statement about the Sony. I would need to see it and read some reviews. The general word is always the same that LCD displays can look nice, but they won't be as good as plasma for image quality, and the better LED/LCD displays almost always carry a pretty significant pricing premium to get that quality look. So, I wouldn't expect as much image quality from the Sony for sure, but they do deliver a well built piece of hardware.
I would not consider DLP. Even less since it seems that Mits. is getting out of that business.