So, jokes aside, I had a chance to listen to the production HM-901 today and I do take back my previous thoughts of what I heard with the May '12 and Oct '12 prototypes. This production version did grasp my attention but admittedly it's with their tracks, not mine. I tried with my Tralucent 1Plus2 earphones. It won't be fair to comment on the sound since it was so short and it wasn't my tracks.
But I can comment on the shell, and at least from memory this product does feel more robust than the early prototypes. Kudos to Dr. Bian on this product.
HM-901 amp board. Looks like an AD8397 on this one (Model's hands: Frenchbat) :-