When i worked at JB we sold narta (National Associated Retail Traders of Australia) warranties. The first trick is that if you got a 3 year extended warranty it does not make it 4 years total (1 year manufacturer). It added 2 years to your existing warranty. Secondly the narta warranties replicate the manufacturer warranty, so whatever 'brand x' cover narta will do the same. Thirdly, they do actually have a lemon policy which means if they try to fix the problem 4 times they just replace the unit. You can also buy the warranty up to thirty days after purchase, to give you time to think.
I'm still to work out if extended warranties are worth the extra money, i can't answer that question to myself even! However, if i was to buy a no-name brand television i would buy the warranty. I never had any complaints from customers regarding the narta system with dealing with them although i can't comment on their service. It's just like Apple i suppose, sometimes excellent, sometimes terrible. The question about value is also hard to answer, if you use the warranty it's great value, if you don't then it's not good value. Although how much is piece of mind worth to you?
By the way, the entire system may of changed at JB regarding warranty, get a brochure from a sales guy and have a read
I've tried to answer your question the best I can, however i still don't know about these warranties. It is almost a type of gambling