Most of the content is available on Youtube, but many creators have some extra videos and/or release videos days to a week earlier on Nebula. The majority of the content is video essay style videos and educational stuff, if that isn’t your speed it might not be for you.
The app is easy to use and allows for downloading videos for offline playback. It also doesn’t have any pre/mid roll ads, and many creators don’t include baked in sponsor spots either.
The biggest drawback in my opinion is that they don’t support comments.
I’ve been really happy with it, see if you can get the nebula/curiosity stream bundle advertised by lots of different creators. For something like $20/yr it’s great value and also helps provide a bit of less variable income for the creators that use it!