I don't get why people are so impressed. It's pretty obviously staged, not freestyle, and the beatbox is horrendous. They needed three people to do that? Okay, the part of the video that doesn't directly involve the "freestyle" is worth a chuckle. But it falls into the category of "yet more stuff on youtube that's I'm only watching because I'm bored at work."
This is better:
http://www.youtube.com/watch?v=JzqumbhfxRo