I love em'. *Sometimes I don't think they are hard enough. *8 strings might help though to get some more evil injected into their sound.
Personally if you want to have hard vocals in a song (deathy) then I'm cool as long as it's used as an accent. *I have been listening to the new System of a Down that came out a couple days ago and I think they're a perfect example of tasteful "hard" vocals. *Sometimes their singer is normal and you can make out everything perfectly, then he'll go "ugggggghawgwgrrrrh" through some crazy distortion effect and it works perfectly with the song. *If you like Meshuggah then check out the new System album Toxicity. *It's technical/nu-metal, very cool IMO.
But back to the point, Meshuggah is awesome. *I think what makes their sound harder is the great rhythm changes they have. *Any pause in an extreme song where you wonder where it's going to pick up again IMO makes it 2x as hard. *Pantera uses that technique really effectively as well. *Speed metal with one of the
low strings blazing through the entire song just isn't as hard to my ear.