Micheal, you're right - if HD or other linear medium is the primary delivery then Rec709 or some reasonably similar viewing space is the way to go.
Lucas - it's definitely not a trivial job to squeeze every single drop of goodness out of a Red filmout, and such a breeze to make stunning images with Scratch in linear.
But even though there are probably some complications when grading Red in log, my experience shows that applying the log conversion up front, then grading in a print emulation viewing environment ensures that the colorist has the most control to land the detail where it will 'line up' with the way film responds to light.
I am experimenting with the new raw log space in the Red node settings for a filmout in March - seems really promising. Can you elaborate some on exactly how this works?