I think the goal of running native speed compiled-ish code on the browser in a sandboxed way would be great if it worked. CSS and HTML for "apps" has always seemed like a hack to me. The problem is every single attempt to do this in the past has resulted in a bloated mess. Maybe this time will be different...
I am a believer!
The irony is that with WebAssembly maturing, we will have the revenge of plugins, and stuff like Flash is already being brought back, but hey now it is a standard browser feature.