I have the 4K Blackvues, front and back.
Touch wood, its been fine(ish), no battery issues so far.
However it will occasionally claim it has no SD card, and it will keep rebooting saying it, and then just stop and its fine. Or you can stop it instantly by doing a format on the SD Card. This may vary on SD Cards, I just bought the best one for it from reviews, without stepping into getting bent over by Blackvues extortionately priced SD Cards.
I preferred the Blackvue as its practically invisible, the Thinkware was a bit too big for me.
Also checkout the new Kenwood one, it comes with its own screen, the quality is excellent.