Got mine today, the head tracking in the DK2 is beautiful compared to the DK1.
I managed to get AH going with the Tridef drivers and DK2 in legacy mode. The distortion was a little off (warped edges) and there was some graphic issues around edges (probably coz the tridef drivers are for the DK1), and of course head tracking doesn't work.
Just waiting for someone to update OpenTrack and/or FreePIE...