Assuming you are referring to AMD GPU setups (Nvidia can use HD3D as well):
- HDMI 1.4a can only play at 60hz per eye at 720p, but movies are 24hz, so bluray 3D will work at 1080p. You will want 60hz per eye to play games.
- For 120hz, or 60hz per eye in 3D at 1080p, you need Displayport which I believe Samsung is the only one offering these. I believe they are the 750 and 950 series monitors.
- For Nvidia cards, dual-link DVI is used for 60hz per eye 3D gaming. Even when using HD3D.