Let focus on render HTML page, and later CSS3/WebGL Page.
Most apps may only require render external page. Unity Game may need render some 3D Model in IAP Store and CSS3 UI.
Other modular feature like Web Audio could be move later in priority.
If would be good if some music app can develop as UI on UltraLight and communicate to C/C# to playback music.
Web Audio is extremely handy features but for develop music app, I am rather there is apps focus native experience to deliver better experience. UI is nice candy bar with good performance thanks to creation of UltraLight.
It could be extremely good for notification though.