Does anyone here subscribe to either of these YouTube pay services?

I just encountered my first "This video is only available to Music Premium members" message... I'm wondering how much content is being or has already been moved behind the paywall.

General comments on the services would also be appreciated.

Nothing has been "moved" as I understand it. They used to have a paid service called YouTube Red, which had exclusive content, and have now rebranded as "Premium". I'm sure they have also added more new exclusives as well (which probably happened to be something of interest to you in this case), but the primary appeal of it for me is no ads, offline playback of saved videos, and playing videos with your screen off on the phone (obviously just music would benefit from this).

YouTube Music is intended to replace Google Play Music one day but is just garbage in every way. I don't know what the specific benefits of it are. I get both of them with my Google Play Music subscription since I've had it forever. I did end up paying a couple of dollars more to keep it when they got rid of "Red", but it was worth it to me for the ad free experience. If they do indeed replace Google Play Music with YouTube Music, then I will cancel and go to some other service.