I just purchased a 2013 RX350 FSport a few weeks ago. This is our third RX350 ... first was 2004 (RX330), then 2008 and now this one. My wife and I love them. I always buy extra warranty BUT ONLY FROM LEXUS ... NEVER THIRD PARTY. We finance for five years and I like to have warranty that covers most of the financing period. Lexus warranty is excellent because you can go to any Lexus dealer and be assured a great service and know they will still be in business when you need them. Not so with third party and many are scams. On my 2008, the struts went bad in the fourth year of service and it was completely covered .. I knew two were bad and Lexus, unsolicited, found the other two were bad too and changed them at the same time ... gave me a loaner (brand new RX350) for a week with no cost to me. That's why I love Lexus.
Bottom line, consider buying extra years of warranty but only from Lexus ... never from a third party.
Hope this helps ...
ALAN