Just a heads up from my experience - I have been testing and diddling with this all day. I'm the geek type that will change just one setting and exhaustively see what difference it makes - anyway, I was fooling around with the resolution settings for the 3x crop mode, and forgot that I set it above 1920x1080 - shooting normally it was fine, but when I went above that it would lock the camera up.
Not a big deal - pull the battery and start over.
But...inexplicably this lockup disabled audio recording in the Canon menu. If you go off the wrong path as I did please be sure to verify the audio is still enabled. Got some fantastic footage of the kids tonight, and the audio file (while there) was dead silent. Went through all the menu settings and sure enough, the Canon menu had it disabled instead of the usual "auto".
Just wanted to share my experience. I would like to thank all the developers and testers; the MLV format is amazing and the ability to have accurate, synch able reference audio is a huge benefit. Thanks again guys - think how far you've come since last May.
Another side note - I let it record until the CF card filled up - it shut off "automagically" and everything was recoverable in post too.