How does the X7's third row compare to other SUVs?

I've been researching and was wondering how the X7's third row compares to similar offerings in the market. Specifically, I'm curious about the legroom, headroom, comfort, and practicality of the X7's back seats versus those found in the Audi Q7, Volvo XC90, and other large SUVs. Has anyone had a chance to experience all three?