I'd be cautious because they seem to be having firmware issues. I was wondering about this and contacted GoPro support about it. They responded:
"Be aware that there seems to be a firmware issue with the Hero3: Black Edition that is preventing reliable HDMI output to Blackmagic Designs and Atomos devices. I don't have information on how much longer it will be before this is fixed in a firmware update."
"As a workaround... you may need to convert your HDMI to HD-SDI; use the HA5 from AJA, which is a known good solution"
Sent Tuesday, March 12, 2013
Same with the Silver edition as well.