In the midst of all the rave reviews, I'm going to try to be a little more neutral here.
The more I listen, the more the bass advantage the VC has over other headphones stands out. The low frequency transients beat everything else in my lineup (HD800 eq'ed, X00, 650, Aeolus, Atticus, Srh1540). It thumps a lot harder at lower volumes, so you don't feel too much need to crank up the amp. It's also much more of a thump than a rumble. The 1540 also has very good impact, but the bass attack is much different. The VC slaps with drums while the 1540 will shake.
The mids and highs are a bit more complicated.
The Atticus is really dark compared to my others, and the signature ZMF house sound is very prevalent. The 650 'veil' is a consequence of its vocals not being extremely forward, and the Atticus is basically veil x5. I actually don't mind it, and it works well for certain genres. The VC is somewhere in the middle. At least there doesn't seem to be any glaring flaws in the mids, like FR holes. Of course, it still sounds like closed back mids, as there's something to do with free air flow and pressure that allows open back mids to usually sound more natural. I like to call it seashell mids, because closed backs all sound like you're putting seashells on your head to some extent.
The 650 treble is more velvety than the VC, and the 800 treble is much sharper and metallic (bad without EQ imo). The VC treble is both smooth and sharp, but it feels like there's one or two holes in the frequency response. The best way I can describe it is if a headphone's treble is completely smooth, it would go from dull -> smooth -> sharp. The VC sometimes sounds dull and sharp at the same time, but it's not deal-breaking. The 650 probably has my favorite treble response in everything I've tried.
All in all, I'm satisfied. The ironwood comfort is decent with dekoni nuggets, the wood and metal is beautiful, and the bass is TOTL. The mids and highs aren't anything special IMO, but they are competent. They sound less closed than my other closed backs, but still not open. I hope the VC paves a way for headphone designers to not race to the bottom in terms of driver weight. Physical vibration and air movement give the VC its special feel, something that I have not experienced in the planars I've tried.
EDIT: Actually, it seems like the treble peakiness was something to do with the songs I was playing. It's actually very smooth for most tracks.