For 2008, the keys come with stickers with 1, 2, star, and some other shapes. The manual says that the car can be programmed to recognize the key and set the seat settings but there may be some flukes as others mentioned.
Pushing the 1, 2, or 3 seat buttons moves the seat to the correct memory setting but can be pushed once with the car door open (like before you sit down) or pushed and held down if the door is closed and you are seated.
The rear view mirror doesn't react to the seat settings. I happened to notice that position 1 works best with the mirror in the day position and position 3's driver likes it in the night position. This is purely by chance. The night position works with the other driver at night but the position 3 driver doesn't have a night setting because the mirror is adjusted to be lined up optimized for daytime use when in the night position.