Good news, developers and bleeding edge enthusiasts! If you're planning to enroll your Google Pixel to the Beta Program for Android O, the Daydream app and its connected experiences are still available to you. There have been similar previews in the past that disabled access to VR services out of concern for performance issues, but clearly Google feels confident Daydream performance hasn't been negatively impacted which is great.
That having been said, be careful. Betas are often very unfinished, and there are a lot of things that could negatively impact Daydream as you explore this new version of Android.
How Android Beta Programs Work
Google's Android O Beta Program allows anyone to enroll a supported phone into a special update list, where those enrolled phones are invited to download system updates with new software onboard. These Developer Preview Builds include early versions of new software and features and APIs so developers can make sure their apps are ready for consumers when the final version is ready to be shipped to everyone. It's a great system that has made life a lot easier for developers in the past, but everything you see here is unfinished and possibly buggy.
While Google works quickly to release new versions of the Developer Preview with fixes to problems and even more features, nothing is really "finished" until Google uses this new version in its next phone and updates the existing phones.
Because things can be a little messy and some people can't help but try shiny new things even when they are not a developer, Google includes a way to un-enroll from this program and return your phone to a normal operating state on the current version of Android. If you need to do this, the update that returns your phone to stable Android will wipe all of your data.
Is it really safe to use Daydream in Android O?
So far I have tested 15 apps for at least an hour, and the experience inside Daydream on the Android O Developer Preview is identical to Daydream on my second Google Pixel running Android N. Motion tracking is still flawless, controller tracking is the same, and all the apps load just as fast and nothing seems to be missing. As far as I can tell, it's the same experience.
That having been said, Android O itself is not nearly as smooth in a lot of other places. My Pixel has frozen in several places over the last 24 hours, once requires a full reboot of the phone to restore functionality. Things like rapidly switching between apps feels a little sluggish in places that are normally much smoother on this phone. This is likely a result of unfinished software and unfinished featured not being completely ready for prime time use yet, and so far none of these concerns have been experienced in Daydream.
If you do experience sluggishness or freezing in Daydream on Android O, the most important thing to do is remove the headset immediately and close the Daydream app. That kind of stuttering and freezing could easily cause symptoms similar to motion sickness, which is something no one wants.