I'm over 100 hours into listening to these, and I'm in love with them. Listening with a Fulla Schiit out of a Macbook Pro, mostly with Deezer high-quality (CD-level) streaming, which is great, other than the omission of certain artists and labels (Thrill Jockey especially). The brightness that I complained about initially has either dissipated from burn-in or my brain/ears have adjusted, but overall these are some of the best-sounding transducers I've ever listened to. They have incredible soundstage and imaging, massive reserves of bass, and don't seem to exhibit any real weaknesses. They sound fabulous with the Fulla Schiit but are also terrific directly out of my iPhone 6. I replaced the stock cord with a MediaBridge 4 ft cable because the stock cable is so long. Perhaps just as important, they're *insanely* comfortable, and I can keep them on my fat head nearly all day long at my desk without fatigue. I find myself hanging out longer at my desk than I'd otherwise do. I'll probably get fatter as a result.
Someone asked for songs that sound particularly good with these cans. Some of my "reference" tracks don't sound quite as gorgeous as I'd like (Steely Dan still seems a little bright for me), but here are some tracks that really shine for me on the X2s:
Caribou: Can't Do Without You - www.youtube.com/watch?v=BI2Et19vDCM - If the production on this song doesn't send chills down your spine, you may not have a spine to begin with. This track is complex and lush, and develops and opens up like a flower, the soundstage expanding and swirling around you. Amazing stuff.
Steve Lehman Quintet: ArtificialLight - Any track on this record shows off the athleticism of the X2s. Almost all of Lehman's stuff bounces around with complex movements and improvisation, but this one just burns with intensity. Drum imaging is tight and accurate, the bass pops and slaps like you're sitting next to it, and the horns sound sweet and smooth (they're actually further back in the mix than you'd expect).
D'Angelo: Ain't That Easy - https://www.youtube.com/watch?v=lZoxdPGu_4E - Like the Caribou track, this one expands as you listen to it; it's got this strange, almost oppressively bass-heavy claustrophobia at first, then it opens up with crazy vocal overdubs that dance around your head and funky guitar licks that pop up all over the sound stage. It's incredibly dense production and could easily turn to mud on less accurate cans. I can't even imagine how much weed went into the production of this record.
A few others, briefly: The Clash: London Calling - This remaster sounds incredible on the X2s. Destroyer: Kaputt - Another fabulously produced record with beautiful horns, swirling synths and spacious, beautiful imaging; a real gem. Run the Jewels - Oh My Darling Don't Cry: The X2s have no problem with any hip-hop, but El-P's production is always dense and challenging, and this track has that same expanding sound stage that these headphones seem to excel at presenting (not to mention noggin-shredding bass).