Anyone shooting with the cheap Yi 4k camera? I did a little reading on it and it looks like they have fixed more than a few things, but just wondering if they were able to get live HDMI working, and if so how bad is the lag?

Things they fixed but have not updated in the sales info:

Manual WB
Manual exposure in video modes
Additional bit rates
Something about AF in video modes

Things that can't be fixed:

Audio input! There is none provided, would need to hardware have this for confidence audio from your dual system. It's AAC compressed so not really good enough for much of anything anyway. There are similar hacks on the web, concentrate on attacking the microphones to make a connection point.