As what i've read somehere before, only XFX 5770 has some issues running Mountain Lion out of the box, though it runs pretty well with the older versions of osx. Im using XFX 5770, get pass with this problem without patching its bios by pluggin another card on the second slot while using my card as main display. Gaming is better in windows i guess and i was able to play bf3 at max though the temp really spikes up. Havent tested HDMI, sorry.