With the news of the clean HDMI out, I have been searching for different external recorders. I know about the atomos ninja, but was wondering if this product would work as well...? thanks!!
http://www.markertek.com/Video-Equipment/Digital-Video-Recorders/Blackmagic-Design/HYPERD-PT2.xhtml
Paul - I posted in a different thread wondering something similar. I currently have the alpha version of Magic Lantern loaded on my 5D Mark III and have played around with the HDMI out, but do not have a recorder.
A couple of things that I've thought about with regards to this. First, with the Hyperdeck Shuttle, you must have another monitor in order to use this with the 5D Mark III, currently (unless you don't mind not seeing at all what you are shooting

). The 5D Mark III currently disables the built-in LCD when there is an active source connected to the HDMI port. Fortunately, the Shuttle allows for a loop-through external monitor to be attached. Second, the 5D Mark III currently outputs 1080i (at least according to my monitor and LCD TV that I've tried it with). Whether the 24p flag (or a 30p flag) is sent through this output is not clear to me. Hopefully, someone can clear this up. Recovering 24p from a 1080i stream can be easy if the flag is set. But, if it is not, it is my understanding that it is quite painful.
Regardless of how the 5D Mark III currently works, I think it remains to be seen how it WILL work once the new firmware is released.