I only noticed it in FF15, but it may have been there for longer. Change pdfjs.disabled to false in about:config (followed by a browser restart) if you want to turn it on. Here's a test file[0] should you wish to test it out.
I've been using pdf.js for a while on my Windows box (where it is enabled by default on the FF beta channel) and it has performed remarkably well. Sometimes it's a bit slower than Adobe Reader or messes up colour or formatting, but on the whole I've quite enjoyed using it.
Sweet! (It voids the non-existent FF warranty though...)
What's better is, it allows the (awesome) extension Pentadactyl to click the buttons in the viewer (since it's part of the browser). Have to click on (or tab to?) to the document itself though, in order to be able to use keyboard navigation on it though :-/
I've been using pdf.js for a while on my Windows box (where it is enabled by default on the FF beta channel) and it has performed remarkably well. Sometimes it's a bit slower than Adobe Reader or messes up colour or formatting, but on the whole I've quite enjoyed using it.
[0]: https://svn.torproject.org/svn/projects/design-paper/tor-des...
Note that the text in [0] doesn't scale properly, and the page previews in the navigation pane just show garbled text. Usable, but only just.