Pros: Soundstage, natural slightly warm mids
Cons: Bass is there but not particularly engaging
Without a doubt, the MA900s have the widest soundstage that I have ever personally experienced. To provide some context, I don't think my personal soundstage processing is particularly sensitive at all (actually I would characterize it as bad). In many instances, I can't discern the difference between headphones that many others notice significant differences between.
When I 1st put the MA900s on however, it was an eye opening experience for me - the soundstage was wiiiiiiide - immediately and easily discernable.
Comfort is very good - better than anything I have owned with the exception of Koss PortaPros (very light, low-pressure on-ears).
Highs are bit rolled off, but not lacking too much detail (for me - I experience fatigue easily with aggressive highs - not an HD800 kind of guy). Mids are a strength, leaning slightly towards warm. Bass is there. but not particularly engaging, depending on the style of music you are listening to. These are not LCD-2s 8)
Almost perfect on something like Phildel (highly recommended), lacking somewhat on bass-heavy EDM (Subfocus).
I find myself using these a lot simply because of their comfort - if you are looking for a headphone to listen to for hours at a time, these fit the bill (I have a small male head but fairly large ears - 70mm.