If you know you want to keep it then it is a good idea
if you know you want to sell it ,it is a good idea
It is not because it is a Lexus but because it is a piece of mind in newer territory than other cars.
Either way if you sell or keep it then you have less worries since the price of the warr is probably one component and labour alone ,never mind future repairs if needed.
For under $2000 it is a steal
I know if i wanted to buy a 2006 400 in 2010 i would choose a higher mileage more expensive one that still had factory issued warr over a lower mileage one that already ran out.
On other Lexus it is not that important but you have a special one that could need to be updated to revised parts later as it is still a product in testing in ways.