Buy the warranty! but wait until it is almost out of basic warranty first. You can buy a warranty up until that point without needing an inspection. And if the warranty company lets you buy one after your warranty expires and does not require an inspection, run from that company.
Now the thing you need to do is find a good warranty company. Make sure they are indemnified in your state so they cant go bankrupt on you, make sure you have wear and tear coverage, that is a big deal. Make sure it is cancellable and transferrable and what the limit on repairs is. All warranties will have a max on repairs and that will go fast if you have a well equipped car and some issues arrise. Oh and if you do buy one, always save every service record and do them by the book.
If you are still on the fence when the time comes up. Drive by the Lexus dealer and look at all the cars in service. They are not all there for oil changes, they break and when they do it is extremely expensive to fix them.
hope this helps
Danny