I got my x00's the other day and I haven't been able to take them off. I thought I'd share my thoughts on them and compare them to the others in my collection. As a preface, I currently own the following headphones: HE-400, Maddogs 3.2, and DT990 Premium. Each has qualities I like. For instance, the bass in the HE-400 is tight, deep and accurate - but the comfort really sucks. The DT990's comfort is almost unsurpassable, but the highs are very sibilant. The Mad Dogs are comfortable and their sound signature is the most neutral - tending to the warm side. But, by the same token, they are not very exciting.
Now, with that background, I can say that the TH-X00 is at least as comfortable as the DT-990, with deeper (but a bit less accurate) bass than the HE-400, and with a similar sound signature as the Maddogs. Consequently, I'll be selling the maddogs and the dt-990s (asking $ 175 md's and $ 150 dt's - i'll post up a thread over at FS).
I'm keeping the hifiman because they are open-backed, and their soundstage is the best out of all the phones i own. But while the X00 is closed, it doesn't sound stuffy. I guess the best way I can describe it is being in a sound-treated audiophile room. It's really good, in its own sort of way. For those with spotify, a good song to hear this is Hands of Time by Margo Price. You can hear the soundstage as it was baked into the song itself, not as an effect of your headphone. Focus on her voice. I'm also sure that Steely Dan (notoriously obsessive producers) would approve of how this phone plays "Aja."
The bass. Oh dear lord the bass. The X00 provides this in massive amounts. There's no distinguishable "boominess", just a lot of detailed bass. Just listen to the sub-bass in the entire "Fat of the Land" album by Prodigy. Also good is Allan Rayman's "Hotel Allan" album, and "Nu Beginningz" by Congo Natty.
Detail retrieval in the X00 is balanced. I won't say it's "analytical," because it's truly not. I think balanced is a better descriptor, in the sense that you get detail across the entire spectrum (bass through highs) without any particular band being obnoxious. Combined with the comfort of these phones, it's pretty easy to melt away and just enjoy music for hours. For instance, just listen to Etta James' "At Last" - old recording (which can be annoying in analytical headphones); instead, the detail in all the instruments is there without sibilance. Awesome stuff.
The only negative with the X00 is the damn cable. It's about as thick as a transatlantic data cable, non-removable, and the termination is 1/4''. So yeah, it's annoying. But you probably won't be using these on the subway. So whatever. I care more about the sound anyways, and on that point, this thing blows anything else at its price point out of the water. Also, the wood cups are beautiful.