Between my oldest son and my younger brother I've heard plenty of Slipknot.
To me, it's not good.
I've seen a couple of their videos, and agree. I can't take anything away from their energy and the enthusiasm their fans have when they are performing, but it all goes wrong for me when the vocalist starts singing.
The drummer has a unique style though, some folks think he's fake because there are other percussionists helping out but what he does is cool and takes skill.