Realistically, you should be scared when there is a new /back-end/. The front-end doesn't do much. When they change the rendering engine (which they didn't) or

Realistically, you should be scared when there is a new /back-end/. The front-end doesn't do much. When they change the rendering engine (which they didn't) or the javascript VM (which they did), then you need to extensively test it.