If you plan to keep the car for longer than the standard warranty.....the 'Lexus' extended warranty is worth considering. Also (many don't realize) but you can negotiate the price of the extended warranty.....so just a heads up (you should be able to get them to shave off several hundred dollars off if not more). Make sure the warranty takes effect when the original warranty expires, not during the original warranty.
Accessories like the all weather mats & the body side mouldings that are offered (plus any others you are thinking about), tell them you want them for cost up front. Make sure all of this is put in writting on the bill of sale.
Don't be afraid to fax or phone several Lexus dealers near you & ask them for their best price....let them compete for your business, because it does not matter if you take you new ES for warranty / service work at the dealer you purchased the car from originally. ;)
Good luck & keep us posted. :)