Got M-80 and becomes my every day headphone since early this year.
 
I don't like the stock cable with phone control buttons so I make a custom OFC cable, sound is a little bit improved and become smooth.
 
Most of the time I am playing 40% pop, 30% jazz and 30% classical, not so many dance music.
 
Today I brought an album "Random Access Memories" by Daft Punk, this is the number one album recently on many charts.  I know why, the sound is so rich and dynamics with M-80 , make me rock with music, and I never think M-80 can deliver this level of sound at its compact size.
 
Highly recommend M-80, it is all rounder everyone knows, it even works on electronics dance music!

M-100 is a very easy to drive headphones.  Before that I am using M-80s on-ear, and really do not belive any headphones can replace it.  As the M-80 can deliver very high quality audio even with bare iPhone 4S with lossless music tracks!  With an headamp the sound is just bigger and better a little bit but it is not 'day and night＇difference.
 
The first hour I tried M-100 I found the bass a bit too much, maybe I have used to M-80 sound.  But after a few tracks I feel that all music becoming more rich and help me to get higher involvement.  And to my surprise that almost every types of music I like including classical music can deliver same nice feeling.  I always think that classical music should be lean and I always use Senn HD800 for classical.  Now I know that it is not a correct approach, v-moda + classical = BIG SOUND.
 
And of course, for pop music, v-moda is a sure winner, my recent flavor is Adele's "someone like you", it is live version "live at the royal albert hall", the part that everyone is singing together with Adele, it is reallllly shocking!