I had to look for this one so that I could give it a test in person before buying.
I have to start off by saying that the original Guerlain Vetiver is probably the closest thing I have to a signature scent. It's clean and soapy - and has that tobacco sweetness that gives it a bit of sexuality.
Vetiver Extreme is darker and smells a bit dirty - which is cool because I wanted something different. The grass is much more present here, and the absence of the tobacco is noted without question. It feels a bit naked for a few hours.
I would not reccomend this one to others becuase it is an acquired taste. I like it, but it's not mainstream...and casual cologne wearers would think it's a bit harsh.
It's somewhere between the original Guerlain formulation and Encre Noir. I can guarantee that I am the only man in a city of 70,000 that has this in his cabinet and actually wears it out. That's also a good thing.