Plenty of amplification.  Also works great as a line out from my lap top to my integrated amplifier.  Sometimes, after an hour of use, I hear horrible digital noise/jittering.  The music is completely unrecognizable.  I'm going to contact the manufacturer because I think I need to send it in for warranty.  Issue is more prominent on android.  Doesn't feel warm to the touch when it's happening so I don't think it's overheating.
 
When it works I'm very pleased.  When it doesn't (which is almost all of the time on Android after an hour of use) it's useless.
 
Canadian resellers don't sell it at a very fair price (much more than after USD exchange).  Amazon.com won't ship it to Canada.

Bought from Memory Express in Canada for about $220 CAD.  Don't overpay, these can be found for around $250 if you search around.
 
Sound impressions:
Measured with a UMIK1 and the response is very linear with a smooth increase up to 1khz then a smooth decrease back down to 20khz.  Can reach as low as 10hz with a tone generator (can't hear it but can definitely feel it on the skull!).  The sound is incredibly spatial!  Live music (concerts, orchestra) sounds amazing!  Songs with reverb sound awesome.  Can hear a lot of detail.  Very linear audio and if you're into equalization (or tube rolling) these things have a lot of diversity available due to the linear response.  Can make them sound like anything.
 
I've grown to love the sound.  I listened to an assortment of grado & beyerdynamics headphones at a local shop on various amps and preferred these to headphones over $2000.
 
Amplifier Requirements:
These are not efficient headphones.  Needs 150mw at 64 ohms and headphone/phone jacks can't do that.  Don't buy these headphones unless you plan on getting a half decent headphone amp.  Not even my fiio X1 can drive these things.  I get good amplification from the following items I own:

1. NAD 326BEE integrated receiver headphone jack
2. Audioquest Dragonfly 1.4 Black (connecting this to android makes it my most portable amplification solution)
3. Little Dot I+ Hybrid Tube/SS headphone amp (amazing combination!)

 
I highly recommend the Little Dot I+ Hybrid tube amp if you're looking for a headphone amp and don't want to spend a lot.  Get it with the 6CQ6 tubes which pair well with the headphone's audio signature.
 
Comfort:
Large ear cups are comfortable even with glasses.  Headband feels "hard" and tight and can become painful after an hour of use.  Spring is a little too tight.
 
Upgradeability:
I haven't done it yet but supposedly these can be easily modified to have a balanced audio jack for balanced outputs.  The 3 conductor mini-xlr jack is replaced with a 4 conductor, soldering separate negative/ground terminals on two separate conductors.  Then order a 4 conductor balanced cord with mini-xlr for the headphones and whichever balanced connector on your headphone amp.  That's a nice feature in case I move to a very high end headphone amplifier.
 
Supposedly can open up the side covers & slip in some cloth for a little more bass and a little less spatialization.  Haven't tried that yet.

I ordered the Little Dot I+ through Massdrop and got about 30% off the regular price.  I skipped the stock tubes because I heard poor reviews about them and instead opted for the 6CQ6 which are supposed to add a fair bit of warmth.  The warmth is definitely noticeable which is great for my AKG Q701 headphones which are pretty sterile (yet accurate).  They help a lot with the tapering of the bass for these headphones.
 
Paid $102.99 from Massdrop including the upgraded tubes.  I should have bought two!
 
I have them set to the high gain setting and have listening impressions for the following outputs with the 6CQ6 tubes:
 
 
The instructions detail how to change the jumpers & dip switches but don't give instructions on how to open it up.  Only need to remove lower screws on front & back plates, no other screws.  Tubes are cool enough to touch but unit itself is almost too hot to touch after an hour of use.  Hissing & crackling goes away after an hour of use.