I've got a DK2 but I've not used it for over a year now. If memory serves me correct, I think it was pretty rubbish when running OS X. As for OS X demos? The sites I used to use are all dead now it seems so I can't really help with demo links. Alas, when I used it last it was almost always via Boot Camp.
I knew development had stopped a while back, but even the demos are difficult to track down. Getting the hardware basically for free, so thought I might tinker with it.
As the cMP folks can attest, this old thing FLIES. Even on a 4k monitor WoW and other casual games can be run maxed out. And the VR games.... holy cow it's really neat.
Such a shame nMP cannot do this without major fiddling about.