Google has released the Wear OS Developer Preview software to the public, letting anyone, developers included, take a stab at flashing this new software to their watches to see what the changes will be like when Google finally pushes it out in a more stable fashion. While there isn't going to be dozens and dozens of changes with this build of the software there are going to be some notable changes which you will want to make note of if you have any interest in the dev preview for Wear OS.
The biggest change perhaps, as that this dev preview will bring over some of the Android P platform features to the wearables platform, meaning there will be some things from the latest version of Android that you will now get to access and utilize on your watch. This includes but isn't limited to the capability to have the watch automatically disable it's radios when the user isn't wearing it. Basically the watch will be able to recognize that it's not on your person and it'll disable things like Wi-Fi and Bluetooth, and other radios so they're not draining the battery, which makes sense as if you're not wearing the watch, then there's no real need for it to stay connected and receive notifications.
Another feature to look out for will be the Dark UI System theme. This rolled out to some users earlier in the year but it is also part of the dev preview so those who wish to install it will still have access to it, and it will give developers a chance to test their Wear OS apps with the new look. As before, Google highlights that the reason for the Dark theme is because it was aimed at enhancing glanceability so the display was easier to see and the notifications were easier to read. If you're looking to install this software, there is one fairly large caveat, and that's the fact that right now it is only available for the Huawei Watch 2, or there is also a version for the Android Emulator. Google hasn't mentioned when or if they will expand the preview to more watches.