i put mastodon in the same category as current opeth and meshuggah....bands that appeal to hipsters because it makes them feel like they can say "i listen to heavy metal, isnt it cool man" and also the folks that feel that if you dont "get" the band, they are smarter because "they are so progressive and can play 1/4 polyrhythms on a 20 string guitar whilst sucking on swisher sweets"
yes, i've heard all three and they struck me as nothing special at all. i know im generalizing and i know people really do enjoy these bands, and i know im judging them somewhat on stuff beyond their control and im ok with that