Only because no one has mentioned it, Check out the Symat7 from Exped.
Its highly insulated, and 3" thick. They are pricey, and can be heavier than other pads, but so far I have to say its a great pad. The 7s come with an integrated pump, so you don't have to blow up your pad with your mouth, which introduces moisture into your pad, that can break down the insulating properties.
It has proven to be very durable, and for sleeping on the ground in the mountains, its comfortable.