My home machine, a once wonderful dual-1.0 GHz G4 box, proved not entirely up to the task of watching the HD Serenity trailer. I downloaded everything, rebooted as apparently required, and started it up.

The 1080p trailer wasn't really 1080 scan lines tall. It was the full width of my display (1900x1200) but maybe 700 pixels tall. It rendered at maybe 5Hz, slamming both CPUs. The lower-resolution HD trailer got maybe 10-15Hz -- enough to get lip sync, but not enough to be smooth.

So... unless you've got one of the latest, greatest G5 machines, you're not going to get all the HD goodness that's potentially available. Still, the still-image resolusion is absolutely photographic quality. Stunning stuff.