Me too -- I much prefer the AD over the HD800. To me, the HD800, while incredible with classical and some jazz, was just not satisfying with most other genres, including most jazz, rock, dance, reggae, world etc. etc. The HD800, IMO, had too much treble energy, not enough bass energy, and had a certain "thinness" overall. When I had switched cables on the HD800 to Moon Audio Blue Dragon, which produced a good improvement, it was still not enough to make me love the HD800.
The AD, by contrast, is just so satisfying and sounds so "right" on all genres. While an open headphone might produce some additional air and separation on classical music, the AD is still fine with classical and great on everything else too.
BTW, I also now use a Moon Audio Blue Dragon cable with the Alpha Dog and it has also produced a real nice improvement -- more of everything, detail, transparency, bass, dynamics -- it was like upgrading a major component like an amp. So, if you think the AD is great with the stock cable (which is still a very good and well made cable, using well-regarded Canare wire), wait 'till you try it with something like the Moon cable.
And there must be demand as the AD becomes more ubiquitous since Moon Audio stocks the Alpha Dog (and Mad Dog) connectors.