I'm thoroughly enjoying the HDPs as well. Have had them for approximately 6 months now and they drive everything i've thrown at them, from my previous HD800s to the current Hifiman HE-6s. Although whether this humble DAC/AMP unit does justice in driving them up to their potential is an entirely different issue altogether.
However, it must be said, I have enjoyed every moment with these gems and frankly even now with the notoriously difficult to drive HE-6s, they do an admirable job. If not for my need to see if the HE-6s can do with more power from a different AMP, i would see the HDP staying with me for a long time more.