you should always get the warranty. Best Buy, CC, PC Richard, and stores of that caliber have very good warranty policies. You should read what the awrranty covers of course before buying it, but it should cover a vast range of issues. These TVs are great but they are new technologies. Many people experience some sort of problem with their sets, whether they be plasma, LCD or RPTVs. It is best to cover yourself against any possibility.
I had a friend, just last, week have a problem with his brand new Sony XBR4. He did not buy the extended warranty. His TV was bought in Sep and was just out of the 15 return policy for J&R. He sepent the next 2wks dealing with Sony trying to get the set fixed. He was finally able to finagle the manager at J&R to give him a new one, but it would have been a lot simpler with a warranty.
To give you another example, and the main reason that I bought the warranty, I had another friend that bought an old 55" Sony CRT RPTV from Sears with the warranty. He had the set for about 10yrs or so. During that time period he had the TV serviced for various reasons. All the while he kept extending his warranty every time that renewal came up. The fixed the set many times. The great thing about the warranty is that they state that if they can not fix the set, that they have to give you a new one. Well, the set finally died. They were unable to fix it anymore so they had to give him a new one. Guess what? His Tv was a dinosaur lol. They didn't make it anymore. So they had to give him his choice of TV for the equivalent amount of what he paid for his set originally. Now a 55" CRT may not be worth too much now, but it was pretty expensive when he bought it. So you can imagine what kind of TV he has now lol.
Even without the whole new TV thing, it still makes sense. None of the new TV technologies are without their problems. It is a good idea to protect yourself.
I would also look into getting the set that you want from PC Richard. I believe that their warranty is either less money or covers more years than BEst Buy's. If Best Buy has it cheaper, PC will price match so that shouldn't be a problem. Don't know if you have a PC in your area though. The other reason why I say consider PC is because although they are a large chain, they still have a Mom n Pop attitude, and they are much more open to negotiating not only price, but policies as well. Where as CC and BB have very strict guidelines and such, and are not usually open to bending rules. Just a thought.