Well, I'm a fan of Fear Factory, and yeah, they made it pretty much their trademark back in the early 90's. Of course, that's Extreme Metal, so there you can hear it very, very clearly.
But the point is, I think it makes the drums and the guitar (or bass) sound like one instrument, which is really cool, so instead of hearing the hit of the drum and the note of the guitar, it just sounds like a really punched note. I'm not saying they should do it on EVERY song, certainly not in ballads, but I do think it adds to how powerful a song feels.