Pros: Ultra-present mids, pleasant aesthetic design, sturdy build
Cons: Crowded soundstage, somewhat high clamp force
While generally I can't afford the $1000+ caliber of headphone, I have been lucky enough to demo the Oppo PM-1 and Audeze LCD-3 for the past week at work. That might not be a fair comparison considering the price difference, but it is what it is.
Equipment: Laptop, Vivid Tech V1
Music: Little Dragon - Ritual Union, Sufjan Stevens - The Age of Adz, Caribou - Swim, M83 - Saturdays = Youth, LCD Soundsystem - This Is Happening, Yelle - Pop-Up
Obvious by my music selection, I'm into pop, rock, electronic, bright vocals, and trades between sections of high dynamics and super-density. This is only accentuated by the forwardness of my DAC/amp (which I'll admit isn't the best in SQ, but it's what I've got at work, and sounds decent, especially when you turn up the gain enough to get out of my perceived region of nonlinearities).
My only comparison for this headphone is the Audeze LCD-3 which I've been listening to back-to-back on albums (mix of 320k and FLAC). The one thing that is immediately obvious when switching is the compressed soundstage of the PM-1s. I would put the soundstage width/breadth on the order of my Sennheiser HD 595. It's there, the headphone is making the attempt, but it still doesnt put me in a space as much as I'd expect on a $1000+ pair of cans.
The positive side to this, is that all the mids are gathered and presented right in front of you, all while still being able to differentiate between sounds/instruments. I'll relate it to the forwardness of some of the lower end Grados (I have the 325i), but the sound is far more refined. The one exception comes from The Age of Adz, which features lots of live instruments. Everything was smeared together during dense sections of the recording. It got me thinking -- maybe the other recordings don't exhibit this smearing because they are carefully crafted/controlled electronic sounds that can be highly managed in mix & master?
The other thing that gives clear evidence to the crowded soundstage is listening to Swim back-to-back with the Audezes. The record makes liberal use of instrument panning and fading with great depth. On the Audezes this was almost enough to make my head spin trying to track all the sounds (actually an interesting experience that I hadn't yet come across), but on the Oppos, everything is right there for you to 'see' with a slight darting of the eyes. (I hope that made sense, hah!)
Bass is somewhat muddier than the LCD-3s, but still much clearer than my gamut of $200-400 range phones (K701, HD595, 325i, etc.). Extension is there, impact is there (moreso in the midbass than sub).
Treble is pleasant. The LCD-3s sparkle quite a bit more (which can be good or annoying depending on your preference of music). The PM-1s are every so slightly subdued, I would imagine to prevent fatigue (which they do well).
Overall I dig these cans (except the price). You get a nice wood case, a denim travel case, a shorter 3.5mm cable and a longer, sleeved 1/4" TRS cable for them. Though the clamping force initially felt a bit strong, I didn't feel more uncomfortable at the end of a 3-4 hour listening period than I did when I first put them on. The chamber for your ear is pretty shallow, but everything your ear is touching is very soft.