The guitar arpeggios are nothing short of amazing. That kind of precision and speed requires skill and stamina.
Though I can't listen very long to most Death bands because of the singing style, ("Lamb Of God" being a typical exception), I say that if you're looking for where the best rock drummers, bass players and guitarists ply their trade, it's Death Metal. Some of the musicianship is mind blowing, simply jaw-dropping.
On a related issue, as a former sound and lighting tech, I found those playing metal to be the nicest, most humble folks - decent, too.