YouTube VR is one of the best reasons to use Google's Daydream VR platform, but the company didn't make it available for higher-end PC headsets. That's just ended with the release of a Steam VR version designed for the HTC Vive. It's available to download right now.
I'd love to tell you how it is, but for some reason it doesn't work on my PC — it crashes instantly on start, and a lot of people in the Steam forums are having the same problem. A member of the dev team has responded to the thread and is looking into the issue.
Google has released YouTube VR in Steam Early Access, to be fair, indicating that bugs are to be expected. But having the app not work at all for what seems to be a significant proportion of the userbase is an unfortunate slipup — especially considering how good Google Earth is on the Vive.
Still, at least the app is free, so there's no reason not to try your luck.