First of, good job guys!
Here are my first investigations: it works!
But it's very unstable. I had to remove the battery quite often.
Sometimes I got some noise on the right output (might also be left, maybe i confused the outputs) and the screen turned black. (My right ear still hurts). I can not exactly say when that happens, but it does while I changed some settings. Also, it happens (every time) when I start up the camera with the headset connected. When that happens, the battery needs to be removed (a few times). Changing the mode via the mode dial seems to help, too.
Sometimes the audiometers show sound, but I can't hear it through the headset. When I go into the menu and change the Output Volume setting to something random, it suddenly works.
The Audio Remote Shoot works well as long the headset works fine.
Also, I noticed that the camera, especially when the noise-on-headset-and-screen-turns-black error occurs, gets hot.
There also is an error in the menu. When I try to change the input source, it loops through the different modes. Looks like scroll-wheel-right event is being triggered for some reason.
I used a external mic (røde stero videomic pro) with a totally standard headset.
It's indeed still not usable for other than testing, but it looks very promising - again: keep up our good work guys!
PS: my ear still hurts - an our after having performed the tests.