[Google Pixel XL Guides, News, & Discussion] Taebom:
Here's a few known issues that Google posted with the developer preview:

General advisories

This Developer Preview release is for app developers only for compatibility testing and development. This release is not intended for daily use or . Please be aware of these general notes about the release:

This release has various stability and performance issues on all devices that make it not suitable for daily use on phone or tablet, especially for non-developers.

System and app performance is known to be periodically slow / janky, and device may become occasionally unresponsive. These problems may become more acute with prolonged use.

Battery life may be regressed in this early release for screen-on and screen-off use cases.

Some apps may not function normally on Developer Preview 1. This includes Google’s apps as well as other apps.

Known Issues

Performance and battery

System and app performance is known to be periodically slow / janky, and device may become occasionally unresponsive. These problems may become more acute with prolonged use.

Battery life may be regressed in this early release for screen-on and screen-off use cases.

System UI

System UI crash after toggling screen brightness, then going to Overview (recents) and selecting a new app.

Occasional issues navigating Home, with incomplete transition making the device unusable.

Taps in Quick Settings may be registered in another location.

When using Autofill, an “Android system app displaying on top" message is sometimes shown, but it can be ignored (if it's turned off, it will disable Autofill).

GCM/FCM

FCM doesn't work in a secondary profile unless the app is also installed on the primary profile. If the app is not installed on the primary profile, an FCM token is not generated in the secondary profile.

Developers using FCM/GCM with Android O should updated their Google Play services SDK to version 10.2.1, which is available from the SDK manager in Android Studio.

Android TV

Setting up a restricted profile then restarting the device causes the device to be unusable.

Typing in the search bar causes a crash.

PIP image does not fill the window.

Launching applications via voice command does not work.

Application size is not displayed in Application Settings.

Microphone button on remote control does not work.

Factory reset does not work on Fugu.

Connected remote control device disconnects intermittently.

USB connected drive cannot be formatted. The Setup as device storage formatting option does not work properly for drive attached via USB.

Device may freeze with blank homescreen when plug is inserted.

Location status in Settings may become disabled with user unable to re-enable.

Not able to reorder games in the apps and games row.

Content may not play after relaunching media apps.

Wi-Fi

611 call can’t be made on a Wi-Fi profile.

Voice search and hotword

Occasional repeated action suggestions after hotword detection.

Android for Work

Enabling a Work Profile may cause a crash in Settings app. To work around this issue, remove and re-add the Work Profile.

Android Device Manager

Selecting the Settings > Security and Screen Lock > Android Device Manager menu item may cause a crash. Updating to the latest version of Google Play services will resolve this issue.

Android Wear

Embedded app installation from Play Store can sometimes crash. Side-loading can be used to work around this issue.

Only the x86 emulator is currently supported.

Default watch face complications may not load until you switch watch faces or otherwise touch watch face settings, or reboot the device.

Other

Using the Google Drive app’s PDF viewer to load a PDF document may cause the device to freeze.

Apps or games may hit ANRs in GLThread, such as with AssetManager::open, that cause crash or failure to load properly.

Games using Google Play games services may have problems with sign-in.

The latest release of Android Auto may not work properly on Developer Preview 1.

The NDK cannot build targeting Android O DP1 (an upcoming r15 release will fix).