Brill, it's running on Steam on a MacBook Retina with OSX as up to date as can be.
As a quick test I just downloaded the non-DRM version and put it on my Air w. up-to-date Mountain Lion and it worked beautifully (yay), so it's not pervasive. Can you send me details of the machine it's not loading on, and if there are any crash reports or error logs send those too? The address is support at sidhe.co.nz