The timing of Tyl's review is interesting given that I just pulled these back out a couple days ago and decided to give them another chance. I purchased them when they were released and did let them burn in for about 10 hours before deciding that they were good, but not as much so as the PSB M4U2 I've been rocking for a few months. I also got the M100 recently as well and still the PSB in active mode were my preferred headphone.
I pulled the Momentum and the M100 out a couple days ago and decided to give them both more burn in time, so they've both got close to 60 hours on them now. Oddly enough, the M100 didn't change all that much with the extra burn in, I still enjoy it alot but still think the PSB is the better headphone overall even though I like the styling and fit of the M100 better.
The Momentum was a different story though, they're like a completely different set of cans now. One thing I will say is that on the first go around I had some bad sinus issues, but those same issues were there when listening to the PSB as well, and even with all that I CLEARLY preferred the PSB. Fast forward to today when I got some time to listen to them post burn-in, and these Momentums are absolutely spectacular.
I've spent the better part of the evening switching back and forth, and honestly think I prefer the Senns over the PSB. They're very different cans, and my preference is not by a mile, but overall I think I like the Momentum better. Compared to the Senns the PSBs do sound a little forward, they're not bright by any means but are a tad more forward in their presentation. It's odd, but these two cans sound completely different, and yet both sound so good, and further still my preference of one or the other is not by much.
I suppose if I were forced to chose I'd go with the Senns, but thankfully I don't.
Basically, I agree with everything that Tyll said in his review. I don't think I have the experience and have listened to enough cans to say how good these are in the grand scheme of things, but these are VERY good and right now are one of my favorite headphones.
So I guess I'm not really adding anything new here, just repeating what some have said already, these are some really great cans.