HDR is essentially useless. It works by shooting two differently exposed 30 fps images simultaneously using the 60 fps capability and then superimposing them together as a single frame @30fps. Unfortunately, it seems unable to properly register the two frames so you end up with an out-of-sync double exposure. The problem is in the processor chip-set and so Viofo is currently unable to do anything to fix this. Hopefully, Novatek will come up with a fix-it at some point.
I find the camera works quite nicely at 60 fps with HDR off and the exposure turned down by -1/3 EV.
I noticed that I experienced the pulsating banding problem in low light with V2.0 that another member complained about. These days I don't drive at night too often and I live in a rural area where much of my night driving is in pitch black conditions anyway so the problem doesn't really bother me too much (for now) and bright headlights overcome most of the issue where it counts. (@viofo really needs to fix this problem, however - hopefully soon)
This is what the HDR double exposure problem looks like in V2.0.