They are loud, I wouldn't say "very". Using a DB app on my iPhone my background noise (light off) was 44dB and 1ft away from the light when it was on was 59dB
There is a slight flicker, at max FPS (21.65k) it dims every other frame. You can't see it if you playback at 60fps or capture at a lower rate
You can power it with a battery and chain them together which is pretty cool, i'm using an AC power supply he provided