I'm not having much luck with the DK2 so far. The test scene in the config utility works fine, as does the tuscany demo in the SDK but nothing else seems to work.
If I try any of the demos that people are generally saying work with DK2, e.g. Helix coaster, DCS, etc I see stuff load up on the monitor but the headset just stays black. I've tried direct mode and extended mode, doesn't seem to make much difference.
There's a few things I need to try out from reading around: test with DVI adapter rather than HDMI, append "-adapter 1" to unity demos and look into this directtorift.exe that people are talking about.