TX Lexus, thats a loaded question :) You ask if its worth while buying a Lexus extended warranty? If you future repair bill exceed the cost of the warranty, then its worth it. I know thats a stupid answer but an extended warranty is a insurance policy, the cost is already calculated with the risk. If every Lexus is the same, then one can answer a simple yes or no, but it is not and everyone have different experience.
A lot of owners have been having problem with the rear air suspension on the older GX. The two height sensor slone is almost the cost of the extended warranty. There is a guy name troy out in Toyota of Springfield MA selling Lexus platnium warranty for about $1800, 7 years, 100000 miles. If you do a search, you will find more info. Good Luck.