Seriously thanks for all the info mate you've been a great help. I guess 3d gaming over hdmi is still a real niche market as there so much less information regarding it compared to standard gaming. With all the people stressing over image quality at 1440p you'd think there'd be more concern at 720p where it makes a far more visible difference. I guess it is just accepted that standard 720p is the best you can currently get over hdmi.
The lack of downsampling with nvidia 3dtv play is a nvidia driver limitation it appears. The hmz t1 can accept the standard frame packed 3d 720p60 (1280x1470@60hz)and 1080p24(1920x2205@24hz) signals no problem and the nvidia card can output them as well. I can set these resolutions so they downsample as well so in theory any hdmi 1.4a device should be able to achieve this with current hardware it's part of the standard afterall. The problem is none of the 3d drivers available currently output directly to a frame packed resolution. Should anyone be interested the timings are here
I tried the tridef drivers. They work with nvidia cards using 3dtv play if you set your 3D display as AMD HD3D or Direct 3D stereo. If anyone wants to try this to get it to work with a nvidia card:
1) Enable 3dtv play and set the 720p 3d resolution.
2) Set the 3D display in Tridef contol panel to Manufacturer = "AMD", Model ="AMD HD3D Technology(HDMI 1.4a)" or Manufacturer: "(standard display types)", Model = "Direct3D Stereo (60hz)"
3) If you get a side by side display disable 3d vision in game (default keyboard shortcut ctrl+T).
It appears that the downsampling is actually built into the tridef drivers why couldn't nvidia do this! I set my desktop to 720p60hz 3D and then it scales to whichever resolution I set from the in game options. Finally downsampling from 1080p at 60hz! Sadly though there's a massive impact on frame rates from rock solid 60 fps at 720p to sub 60 and 1080p hovers around 35(which is still better than 24!). I guess this comes from running to 2 3d technologies at once. There's probably a way around this. I'm not sure if the tridef drivers to output straight to a frame packed resolution. If not I guess I could tone down some of the settings to get the frame rate up.
The other issue is the quality of the 3D. Borderlands 2 has major issues but this may be down to the Helix\Eqzitara patch
for 3dvision I've used. There's a Borderlands 2 profile on the tridef site so I'll give it a try.
I haven't tried SSAA yet. As you say in theory it does exactly the same thing, although you lose the granularity of setting the resolution, for some reason downsampling seems cleaner to me. As always the setup is different for nvidia and amd. I think AMD have it built into the drivers. It appears with nvidia you can enable SSAA for all DX10 or DX11 games using the tool here