It's much better then some of the other reviews make it out to be. Rated 4 out of 5 stars

It's not a perfect replacement to Adobe reader, but it isn't meant to be. Most of the documents I've used render just fine, and the rare cases seem to be few and far between.
the project initially was just to see if they could build a PDF reader, which they did, and it's probably only about a year old. I see awesome things coming out of this project (and others like it) if it becomes implemented everywhere, just because they've done a lot in a year already.

This review is for a previous version of the add-on (0.2.537.1-signed.1-signed).