Re: No audio from HDMI (MCP89 / Geforce 320M): Reason: no connected devices detected
Which snapshot did you use? I checked alsa-driver-20100806.tar.bz2 and the official patch is there (which admittedly does look very different; search patch_hdmi.c and patch_nvhdmi.c for "old_pin_detect")
Did you power on the Mac with the monitor plugged into the HDMI port? It's possible right now that audio-over-HDMI only works on the port that the BIOS used for boot messages.
Can you please post an "nvidia bug report" after having booted all the way to X, and also a copy of all the eld files.