I agree, very cool topic. I'm not heavily in to down tuning either, but I think some songs just need that "punch". And if/when it's done right, it really works. I really think they have used it properly - where it just sounds right.
Another thing I like is that they use several different tunings. It's not just one "standard" dropped tuning.
I can't say for certain, but from what I saw, Rudi and Matt both appear to be tuned the very same - I was actually watching for that the last couple times I saw them.