Pros: Flat sound, over ear design, eartips hard to get off
Cons: Eartips hard to get off, hard for audio newbies to put on
I got mine open-box off of ebay for 249.99 compared to other prices of 299.99. Couldn't tell the box was opened.
My other and only "high end" headphone was the bass heavy Turbines. Initially, I was disappointed by the 425's as they were really flat and lacked that bass punch.
My friend suggested I burn them in, though I doubt it would do any difference. What I did was listen to my favorite song by Leehom Wang - Forever Love and noted what it sounded like. Because I was still used to the Turbines, I didn't really remember how the 425's sounded like to an extremely accurate level. But I do believe my impressions after burn-in was same as my impressions pre-burn-in. Flat, didn't have the boomy bass.
The cord of my Turbine was dying so I started using the 425's more and more. Like anything, time fixed my brain's inability to accept the new sound. Every instrument seemed to be played as if it had its own speaker, whereas the Turbines sounded like every spammed together.
On a flat EQ using Foobar, it sounds very ... natural. Simply put, the way it should be. It's there, but it isn't overpowering. Kind of cliche, but that's the best way to put it.
If you want bass, however, it can output bass like the Turbines can but more tonally accurate. Using my Samsung P2, the bass output was outrageous. Smooth, round, and free of distortion. BUT, if you want bass just go for Turbines and you will have bass no matter what device you use.
There were some tracks that sounded like the vocalist was singing right next to me. Guitar and other strings sounds decent, but because of my lack of experiment with other IEM, I cannot comment much.
Like many have noted, they could be a bit brighter. If you really want that treble, use the EQ or go for the UE's.
Hard to remove tips mean you won't lose them
Flat sound is preferred for most audiophiles, can produce bass if device is good
Hard to remove tips mean it's pain in the @$$ to remove
Most of my audio newb friends can't put these on without my assistance