Mike Hulmewrote a review of GoPro HERO4 Rechargeable Battery on April 28, 2016
Familiarity: I've put it through the wringer
I was bummed when they changed the battery design from the hero 3 to 4. Hero 3 batteries don't work in a hero 4.
These batteries are just fine. They're the original battery, so expect to pay a little more than no-name brands. I have both, and I can't tell a difference in performance between the GoPro name brand batteries and the no-names.
Either way, I always travel with at least 3 batteries for my Hero 4. When shooting at 4k, it eats up a lot of memory and a lot of battery quick, so it's best to have some backups.