The notification popup UI has been upgraded to UI 3.0. This should mostly feel the same, just slightly more polish on the visuals, there wasn't really much to change with it, notifications should remain fairly simple, and I wanted to ensure that all existing applications wouldn't run into issues with the new UI.
Added the ability to play sounds to the API. This will be documented soon.
Added a subscription tag for notifications to the API.
Overall, it should feel like not much changed from the previous build. The notification popup should just look mildly different. If that's the case, we've got success.
If you notice any major formatting issues with apps that send notifications to XSO, please let me know!