I wouldn't even compare the 7.1 surround on a comparable level to good surround implementations like Creative SBX, Dolby Atmos, Sennheiser GSX. To me, those do a better job at putting more distance in rear positional cues than the Mobius implementation of 3D. However, I'd still say it's a pretty solid effort by Audeze which still works fine. Also, this could be addressed in the final product where the surround processing can be tweaked for bigger sense of space etc. I don't wanna pass final judgement until the final version, since it's still a work in progress. I recently experienced a lot of VSS solutions, and I feel most do well in surround emulation with the difference being how well they can do rear positional audio with varying levels of 'distance' between you and the cues. That and the tonal balance, which are very different with each VSS solution. I still think SBX is overall the best.
As for 3D in STEREO, well, it's actually BETTER to my ears than those previously mentioned virtual surround solutions in STEREO mode for me. VSS solutions tend to sound overly processed and just blows out the left/right channels. 3D stereo on the Audeze is literally like having two virtual speakers in front of you without too much processing in the sound, at least in direct comparison. I'd still choose plain stereo/3D off if all I got was a stereo feed, but there are times when I enjoy the feeling as if I'm just listening to front speakers instead of headphones. The headtracking also helps with this 'faux' sense of having speakers in front of you.