Amazing... This has been discussed in other threads too, with people wanting to turn it off thinking it will keep them from getting stuck if they can spin the tires to get out. The incline test here really shows where that's not true. Having traction on gives you a better chance at going, as it did in the video.
I was worried when he went to test ESP without a helmet and neck brace on. That test could have easily flipped the car, and he's lucky he didn't wind up flipped. (It looked like he got a little whiplash as it was...) I've felt each system trip in my smart while testing it out on the snow and ice up here (usually in an abandoned lot), and on the rare occasion they've turned on in traffic (black ice, etc) I've been glad they were on!