Mine's just burning in, but on first impression, I do like it better than the stock DAC-AH and the modded DAC-AH from diyclub.biz. Mostly better seperation, not hearing much more detail than a stock AH. But then, I've only listened to it for about 5 minutes.
There is a locking headphone 1/4" plug on the back of the DAC. It is digitally controlled by the buttons in front. Haven't spent enough time with the built in amp to really make an opinion. It sounds okay, plenty of power, background is dark, not enough time to tell if its the DAC or the amp.
I will say changing volume is a pain. You have to up the up/down button to select up or down volume, then push the set button to actually change the volume. It does remember the last volume when you turn off the amp.
Bypassing the amp? There's XLR and RCA outputs on back, so just run your IC from there to your amp. Unlike a DAC1, the volume control don't affect the XLR and RCA outputs.
Will post impressions when I spend more time with it.