I think extended warranties are a waste of money. It's insurance that has a low probability of paying off - just like I've been paying auto insurance for 25+ years and have never had an accident.
But, if it gives you peace of mind, make sure to check the terms of the warranty. Many times the warranty runs concurrent with the manufacturer warranty and will explicitly state that the manufacturer warranty has precedence. In other words, your 3 year warranty will start at the day you purchase the TV - just like the manufacturer warranty - and will not be valid until all remedies with the manufacturer warranty are exhausted. So your '3 year' warranty is actually two years and will not cover anything that would be covered by the manufacturer warranty. Extended warranties are a cash cow for the provider but for the consumer, not so much.