To echo my general feelings about the Mad Dogs since upgrading to my HE-6's...
Even though I've found out that the Mad Dogs signature isn't my favorite, wanting a little more treble attack and definition, the general qualia of the Mad Dogs is just one of sweet comfort. I plug em in, put them on, and play something, and I stop worrying about anything else. Having both capable planarmagnetic drivers and a fairly linear representation up until the treble roll-off makes it a pleasurable easy-listen headphone, and the comfort of the pristine alpha pads just seals the deal (no pun intended). It's a sit-back-feel-good headphone.
The HE-6 is the opposite in this regard, where its more engaging, detailed, and tactile presentation call me to attention. It's difficult to NOT analyze what I'm hearing since whenever I put them on, I put them on knowing they're a flagship, that they're supposed to be flawless, and there's an expectation that I'll be "blown away". It's probably because I'm still getting used to them, and perhaps later down the road I'll be able to relax a little more, but for now, I can never listen to music that I want to listen to. I want to listen to the headphone. I believe it was aamefford who voiced himself similiarly in the last MD thread that the MD lets you just listen to the music, and I agree wholeheartedly. I know this is absurdly vague, but it is my thoughts nonetheless.
Throw on some great isolation with the comfort, and you have yourself an ergonomic headphone that sounds great for what it is.
