Rated 5 out of 5 stars

Using standard and javascript cutting edge features, avoid external and third party plugins, like Foxit, Adobe: that are the goals of this Mozilla Labs Firefox's PDF viewer.
I use it every day. It's getting better release after release. And the last build is very cute and good looking.
And from this month, I switch to the development version http://mozilla.github.com/pdf.js/extensions/firefox/pdf.js.xpi to see the day to day evolution.
Thanks Mozilla Labs guys.

This review is for a previous version of the add-on (0.3.175).