Anyway. The extender comes in the usual Canon cardboard box, with the booklets that no-one reads, and a clothlike bag thingie. Smaller version of the one you get with the 24-105L F/4.0.
The build quality is what you'dd expect for this kind of money. Like a tank.
Installing it is simple. First hook it up to the lens, then attach the camera-body. At first it goes kinda stiff, but supposedly thats due to the weathersealing.
Ill be taking it with me on a photo-trip this week. Results will be posted, offcourse.