I've got Nebula. Took 'em up on a deal on an annual sub when Tom Scott started his new series on there.
It's...fine.
It's nice to watch channels like Mr Mobile without adverts, but channels like Not Just Bikes and Mustard already run on YT without ads. Sure, there's an ad for Nebula at the end their episodes, but it's right at the end, so is easily skipped.
Don't get me wrong, there's loads of stuff on there, but discovery isn't particularly easy, and most of it is USA-centric, which doesn't really interest me.