It's more than just a way to avoid hearing a commercial every time you want to play Taylor Swift. YouTube announced the other features of YouTube Music Key in a blog post:
It will also include a subscription to Google Play Music, with 30+ million songs, expert-curated playlists, and in the coming days, the ability to watch many YouTube official music videos right from the app.
It'll also offer offline playback.
If you get invitation to join the beta program, you'll be able to try it out for free for six months, and then pay a discounted $8 a month after that. (I don't know how to get an invite beyond begging for one in the comments, but if I find out, I'll tell you.)
If reports are true, several indie labels have already signed on to participate.
In addition to the subscription service, YouTube basically gave its app a Spotify makeover, giving music and playlists a more prominent position.
This launches YouTube into direct competition with other streaming services like Spotify, Beats, and Amazon. YouTube is now basically offering Google Play music plus other perks, and Google Play is already a formidable alternative to Spotify. This could be a compelling reason to switch streaming services.