Massive support signal from Google last week: the 2016 Founders’ Letter mentions Progressive Web Apps as one of Google’s two investments in the mobile web:
We also continue to invest in the mobile web […] Over this past year, Google has worked closely with publishers, developers, and others in the ecosystem to help make the mobile web a smoother, faster experience for users. A good example is […] Progressive Web Apps (PWA), which combine the best of the web and the best of apps—allowing companies to build mobile sites that load quickly, send push notifications, have home screen icons, and much more.
Service Worker support is the cornerstone of PWA support.
As a Developer Advocate at Google helping with PWA and AMP efforts, please let me know if there’s anything we can do to help flesh out SW support - which I do see running at https://meta.discourse.org when I use a mobile UA.