Note: The entire original review has been mostly deleted and overhauled. These were the first at-least-somewhat-good headphones I ever purchased, and I was way too hyped and knew way too little when I wrote this review.
I bought a pair of these used for $70 (months later, I sold them for my roommate for $50), and for that price and being on-ear they are good headphones. Here's a breakdown of their different aspects:
Build: These are ridiculously well-built. Pretty much all metal construction, and tested under ridiculous conditions. They can apparently even be stepped on, repeatedly, and often still be okay (not that I ever tried that). Based on how sturdy they look and feel, that is seriously believabvle. They are like some kind of armored-headphone.
Oh, and the cables are apparently tested for being able to work after a million bend-cycles. I've been heavily using the second cable from the headphones as an input to my car stereo for over a year, and it still works well.
Design: In my opinion, these things look really cool! The all-metal construction and their shape is very "stylish utilitarian" looking, I would say. Moreover, the covers on the enclosures can be customized with a number of V-Moda's own designs, as well as with any user-submitted design! I never went as far as ordering the custom plates, but it's a very cool option.
Comfort: For me there were some issues here. On my head, they at first seemed to pinch a little bit at the top of my head. However, the excellent build-quality makes it easy and safe to slightly bend the headband outward a few times before each time putting them on. After a few days of use, they adjusted to my head and were comfortable.
Sound and Isolation: These do not isolate very well, of course, being on-ears. But they isolate well for what they are (although not as well as the most isolating on-ears). With the music at a decent volume, most reasonable outside noise is not audible. These will not isolate from somewhat-louder noises like a well-isolated closed over-ear will.
--Bass: These have boosted bass. For how my tastes developed over time, it eventually seemed a bit much. I would almost consider V-Moda's headphones to be basshead headphones, to be honest; if you're a basshead looking for a cheap super-portable and sturdy on-ear, a pair of these bought used is great to consider.
The boost seems to be centered somewhere around 80 to 110 or 120 Hz, to my (not super-precise) ears.
However, like with many on-ears, the bass does break-up (distort) to some audible extent at high volumes (for me, borderline-painful or downright painful). Even at the loudest volumes I like to comfortably listen to (loud end of moderate volume), the sub-bass (on tracks with lots of sub-bass rumble, and with test tones) does sound a bit "muddy."
But overall, the bass does have an impact to it that can be very nice. I imagine people who love bass will enjoy it a lot for this price.
--Mids: Can't hear any distortion in the mids. They sound pretty nice, but a bit congested. Also, the mids don't seem flat, but rather seem to favor the low-mids, so that overall these headphones are definitely quite warm--another bonus point for these for all the bassheads out there!
--Treble: Sounds about the same level as the upper mids, to me. They have a peak at the 10 or 11khz band, which gives these good sparkle.
--Clarity and Detail: Somewhat impeded by the congested sound of these. This is very common for on-ears, especially in this price-range. The detail is pretty good. Micro-details are, as expected, smoothed-out though, sometimes inaudible.
--Dynamics: These have quite good dynamic impact, actually.
--Soundstage and imaging: The soundstage is pretty good actually in terms of width and depth! But, the directional imaging for spatial-separation between elements is slightly "blurred," in correlation of course with the overall congestion of the sound.
Value: Honestly I do not like the sound very much given the resources that V-Moda put into this headphone, as I know for a fact it is possible to get a clearer and less-congested sound in on-ears, especially for the original price of these (over $200, actually) when they first came out. However, this is largely because I am a clarity-junkie. For those who want plenty of bass-slam and warmth with flat mids and treble, with a bit of extra upper-end sparkle, and like good levels of detail but aren't after levels where they listen analytically/clinically, then these headphones are great. Especially for the price they now go for used (in the $70 to $80 range)! I highly anticipate that used M-80's which still work, will continue working fine for years (I bought mine used and it still works over a year later) in the majority of cases, due to the amazing build-quality. For this reason, I give the M-80 a high rating for its value.
Overall: I give these four stars. I don't like the sound much myself, due to the bass becoming boomy and breaking-up in the sub-bass. I also prefer more clarity and soundstage with less congestion, which is possible in on-ears at this price. However, they have a very good value now used, and unbelievably good build. Also, they look awesome! So, four stars. I would put the sound at 3.5 stars (to my ears and preferences) with the value at 4.5 stars, and the build and design at 5 stars. To me the sound is the biggest part, and that's what brings these down to a four-star rating.