So after a load of action filming, and lots of testing, here is my FULL REVIEW of the new DJI OSMO ACTION CAMERA.
Is it better than GoPro?
In some ways yes, in other ways no.
After taking it into the ocean, out at night, mountain biking, filmed in various ways, tested the time lapse, Slow-Motion, 4k, HDR, RockSteady image stabilisation, front screen, picture profiles, U.I., De-Warp, jpgs/RAW, audio/vlogging... Basically tested everything it can do, and compared it side by side to many other cameras (Including GoPro, Panasonic GH5, Sony a7iii, Phantom 4 pro etc...) here is my summery and review of the Good, the Bad and the Ugly aspects of this interesting new action camera.

There is certainly a few things that I have discovered about it that I haven't seen any other reviews covering.
(Like testing out the operation in the water for instance.)
So hopefully this is the one to watch before you go out and buy it yourself.

Feel free to ask me any questions. I tried to be thorough, but I also attempted to not make the review crazy long, so I did omit a few things I wanted to include.

Also, I don't mind uploading some raw clips from the camera, for people to download, if anyone wants that, just ask.

I hope its useful.

Amendment/Additions-
1.Regarding the 'no superview', I should have said, it does allow 4:3 video recording at 4k and 2.7k (without RockSteady) So it is possible to get a wider FOV, but then you would have to squash that image down to fit into a 16:9 aspect ratio. (GoPro's 'superview' squashes the top and bottom, but keeps the centre of shot normal, so it would be a bit of work in post to replicate the effect.)

2. Regarding the TimeLapse in camera video, I should have mentioned that it spits out the video to 30fps!!! Regardless of what frequency you choose. So NO PAL OPTION.
I'm pretty sure they will fix this in a FW update. As to not cater for PAL users is just stupid.
Note, as per my advice in the video, the workaround is to just use the jpg sequence anyway. So its not a biggie as long as you choose both video AND JPG output.

3.In terms of colour, I didn't mention, but if you are looking to cross edie between other cameras, the colours are (obviously) very similar to DJI drones, like the Mavic, and the P4pro. And its not that far from the Panasonic colours (GH5 etc). But the colours are very different from Sony cameras, I have the a7iii, and the colours are significantly different in that to the DJI.