The latest release in the GoPro line of cameras is a further step up of what is already an amazing line of waterproof action cameras. Make no mistake, if you have the $700 (Aussie), have never owned a GoPro before, and you're into action videography, this is THE CAMERA for you. Stop looking elsewhere. Just go out and buy this thing, and you won't regret it.
But, if you are an owner of the Hero 8, is this camera worth the upgrade? Well, it depends. You have a 30% improved battery life (with the caveat that you need to buy a whole new set of batteries +/- a charger) and a built-in front facing screen (absolutely necessary if you are a vlogger). There's also the interchangeable lens which GoPro took out of the 8 (I believe this to be a huge mistake), and all the usual amazing Hypersmooth 3.0, ultra-wide angle lens that takes AMAZING video (now in 5K) and stills.
There is very little to complain about with this camera, except that you can't use the batteries (as mentioned above), nor can you use the Media Mod built for Hero 8 (there is a new media mod designed for the 9, but it's not currently available). This Media Mod is much less of an issue now that the camera itself has a built-in front screen, but you might still want it for the better sound options. This is the part where I got stuck. Having bought the Hero 8 on release, we were promised that there would be 3 mods for this camera released soon after. I know there's Covid, but these mods, to this very day, are still not available (recently they released the screen mod, but the Media Mod that you need for it is now out of stock). That's like 9 months. And the new GoPro has come out before we can accessorise our 8. Will the Hero 9 suffer the same fate? That, I think, is for you to decide.
Let me know if you end up getting this camera, or why you've chosen not to get it.
Have fun!
D