LED bulbs

Has anybody used LED replacement bulbs in their car? They are expensive, but look cool, like the tails in the new Cadilacs, they are supposed to light up .2 of a second quiker, which is 19 more feet of reaction time at 65mph, here is a sight I found with a replacement guide, and description, they also have orange LED turn signal, they look so cool.
http://www.ledtronics.com