Even though I'm quite convinced that this dead horse has been beaten enough, I'm going to chime in anyhow.
I personally think the Omega II is one of the most neutral transducers available. This belief has been reinforced as I've recently gone through the process of attempting to assemble a world-class (within my budgetary constraints) speaker-based sytem. Yes, speakers do some things better than any headphone, but I haven't listened to a speaker system yet that hits dead-on upon that essential "rightness" of the Omega II, especially in the all-important midrange (and I've heard some heavy hitters, lately - Wilson Audio MAXX, Wisdom Audio $55k something-or-other, both of which were, admittedly, in the ballpark, albeit at exponentially higher prices.)
I don't think the bass of the Omega II is at all pronounced; it's certainly less pronounced than the Sennheiser HD 600, lacking the extra warmth that the HD 600 imparts to instuments in the mid and upper bass regions. It DOES, however, ameliorate the thinness that I had previously experienced (to a slight degree, admitedly) with the SR-404 Signature II phone. With the Omega II, vocals and other midrange instruments possess the requisite amount of warmth and color - sounding very natural in consequence.
I also don't think that the treble of the Omega II is at all shut-in, but I may have a personal prefererence for a smoother top-end, as I trust the ears (and wealth of experience) of Vert when he states that the treble may ultimately be a little too recessed in proportion to the rest of the spectrum.
Having said all that, I still REALLY want to hear the MD-R10!! It's a shame that it sounds like Sony is discontinuing it. It's got to be in the upper-echelon of headphones (along with the Stax, Orpheus and yes, the HD 600). I do think, however, that at this caliber, preferences for one over the other can be VERY system dependent. Would I have preferred the SR-404 to the Omega II in the context of a system other than mine? Who knows? Would Jatinder or Mark prefer the Omega II to the R10 in the context of another system? Who knows? But I'm willing to sacrifice myself to try and find out. Okay, here's what needs to happen - Mark and Jatinder need to send me their systems for a lengthy (at least six months) audition of all their stuff, after which time I will provide a comprehensive and impartial review of everything. Also, I will have changed my name and address - don't write me; I'll write you. Whaddya say, fellas? You game?
Lastly, when you are comparing any components of this caliber, all possible elements of chance or corruption in the signal chain that can be removed need to be to provide for an adequate comparison. As much as I laud Headroom for assembling their World of Headphones display, necessary constraints in the execution of said display probably compromised the ultimate potential of all these headphones. Specifically, the Omega II, which I still believe to be the Prima Donna of the headphone world, was probably not listened to under anything resembling ideal circumstances.