I just got my headphones in, but haven't had a chance to game with them yet. Currently listening to music at my desk at work wearing them (a few of my coworkers have given me strange looks because of the big honking microphone sticking out the side) but they're pretty fantastic. They're light enough that I don't think they're going to cause any serious fatigue issues, they're sturdy enough, build-wise, to make me feel comfortable being my normal clumsy self, and they look great (LOVE the black on black on black)
Sound quality wise, I'm upgrading from an original set of Astro A40's, and for the purposes of this semi-review, that's what I'll be comparing to. These were purchased as gaming headphones, not audiophile headphones, but the audio quality is pretty damn good. I like a little bit more punch in the bass, but I can adjust that on the output side. The sound is fantastic. I also purchased the Console Cable from Sennheiser directly so I could use these with my Xbox One. Added bonus, I can use them with my phone now too! These are open back (or semi-open) so there is a lot of sound leak, but the soundstage is fantastic. I'm used to IEM's at work, so this is a whole different experience for me.
Sound Quality over the Astro's: These sound much nicer than my aging A40's, and as many hours as I've gamed comfortably in the A40's, these have already won me over in terms of fit and comfort. One thing I do like about the A40's though is the plate that you can put over the ear cups (with or without foam) to enhance/quiet the sound leak and isolate yourself a little more. That being said, with the PC37x on my head, I can BARELY hear my Cherry Blues on my keyboard in front of me. The more I'm listening to these, the more I'm appreciating the soundstage. It's so much more OPEN than I'm used to, it's both weird and wonderful.
Build Quality: I'm digging the build quality, but you can see a few areas that class this in the more budget range. The gap created by the ear cups and headband when you extend them has some kinda sharp edges to the plastic. Not so sharp that you'd cut yourself, but sharp enough to notice that they aren't rounded off. Is this a huge detraction? Nope. The mic mute function has a nice quiet 'click' when engaged/disengaged, and the mic boom itself feels sturdy and good quality. The volume wheel on the right cup is nice, it works well and there isn't any play or wiggle to it; that being said, it's very easy to turn. This might be intentional, so you can quickly mute or quiet the audio, but my druthers would be for a little more resistance.
The fit is super comfortable for my head. It's got a little tightness to it but it feels like it's going to wear-in a but, so I'm more than okay with how they feel. The ear pads are comfortable as can be. I don't have exceptionally wide ears but I'm tall and have proportionate body parts, so my ears might be larger than others. MDxS seem to have accounted for that; my ears do not touch the insides of the pads above, below or anywhere in between. The headband tension keeps them planted firmly where I want them with no slippage (yet, at least). adjusting them on the fly is a little more difficult than my A40's, but I shouldn't NEED to adjust them once I have them set up right. They stay exactly where they should.
The included cable is of nice build quality. I don't think there's much else to say. The Console Cable I bought separately is comparable (and MUCH shorter, which I wanted). Solid build, wrapped cord, sturdy feeling connectors. The Y split on the included cable seems pretty durable. The Y's themselves have a good amount of room, so I could actually plug the mic and headphone one into my SoundBlaster E5. I wasn't expecting that, so that's nice.
I'm basing all this on just an hour of listening to a couple genres of music, so... not at all their intended use. However, metal, electronica, classical, classic rock, jazz and blues all sound pretty great out of them. I watched a few youtube videos too, and again, I have nothing to complain about with sound. The highs hit right, the mids aren't muddy and while I like a bit more brain-shaking from my bass, theres still nothing to complain about. The deep bass that I'm used to sort of rattling my face is definitely not present though. This is a good thing when I'm gaming, but I'm definitely not going to be replacing my IEM's with these.
My first impressions are positive. I'm gonna hit the sticks a bit over the holiday and I'll report back if that changes.