Pros: A true window into the music: very detailed and neutral.
Cons: A bit heavy and not much clamping. A bit too revealing for badly mastered music.
I got this headphone second hand and have used this headphone for about 4 months now. I've used it with the Stax SRM-T1W, with a CI Audio VDA2/VAC1 as source. I'm really happy with the 4070. It provides the most detailed neutral sound I've heard yet. It truly allows you to hear everything that is in the recording. With some music this is just perfect, mostly with classical and the older generations of pop/rock music. Think Pink Floyd / Roger Waters, Dire Straits, Eric Clapton.
With more recent music it can be a bit too revealing, it won't hide the results of the loudness war and will show you all the faults in the recording to a point that it can be unlistenable.
It's this trado-of that I love: because of the amount of detail it can absolutely destroy some music, but choose the music wisely and you'll be rewarded with a headphone with amazing (maybe unrivaled?) transparancy that is not matched by any headphone I've heard to this day.
Comfort is pretty good, but I had to bend the headband a bit to add some clamping force. Because it uses a self adjusting headband and the headphone is quite heavy it would slide down without the bending.
I like the design, clearly not made to impress the ladies (you can't take it out anyway) but it has a good build quality and the looks compliment the sound. It offers pretty decent isolation because of the closed design, no sound comes out and all outside noise (hard disk spinning, outside traffic) is attenuated enough to not bother me.
It may not be a 'one to end it all' headphone, not if you listen to more recent music, but it is great to compliment a more fun and colored headphone.