I actually really liked what you were doing on Worm of the Dust... I'm downloading one of them because this jerky streaming 56k bit isn't working. I don't see how you guys sound like Mastadon thus far... but that's ok.
The production is a little, not as full as it could be. It seems like there is some seperation from you and the drummer tonally that I don't know how else to explain. On threeve the drummers flashy work seems to be a bit loosey goosey, needs to tighten the screws a bit. But other than that, I think what your doing fits the concept, you don't want to be too flashy in situations like this, and some times root note rocking is what a song needs.
Plus if you contrast doing root note stuff against your "lead" stuff, it makes you look flashier.
Alright, The Lover and the Liar downloaded. The drummers kick is bothering me. I think there should be a tonal role reversal between you two. He's bass drum needs to be bassier/less midrangey, and you need to be a little bit more "low mids" I think. But this is all production notes. I was listening to the song, and I really don't think there would have been room for anything really flashy in this song. I do agree your attack consistancy needs a little work, but I think that's the only flaw with what you're doing.
Good songs, it's not overly my genre. But it's much better than a lot of the... I guess I'll say "alt rock" I've heard in my day... your much better than the band I tried out for who were alt rock... and that left a bad taste in my mouth for the genre. But this is good. Good stuff.