What I'm really looking forward to with this is not PNaCl on the web, but PNaCl as a way of writing high performance portable native apps by using a Chromium wrapper.

I'm very excited by the idea of being able to write an app that "just works" across a ton of platforms using JS and HTML5, with compiled code sprinkled in for performance-critical portions. Projects like AppJS have been working toward this already, but with PNaCl, a big missing piece can finally be filled in.