Since the M80 are the first audiophile headphone I own, this is what I can tell to describe my personal taste.
I love the m80 a lot, though I tend to love boosting the bass and tremble on the EQ. I find the m80 might sound somewhat thin sometimes especially during outdoor use. I guess I'm not that much of a bass head however. I don't listen to hip-hop or rap, but mostly pop and sometimes acoustic, sometimes electronic also but not a lot.
How do the m80 compare with m100 and momentum? I prefer the m100 for the looks and build and cheaper value, as well as my personal love towards v-moda. But sound quality is what I care most for headphones. I commute quite a lot so sound isolation is also something.
I'm not trading my m80 away, this is more like purchasing an upgraded headphone for primary use but I might as well use the m80 sometimes as well.