Update (11/13): MS Office viewer is now broken which means this extension is useless. Rollap and Zoho never worked for me and while the Google Drive Viewer still technically works, the documents are blurry and I can't scroll through the pages.

Awesome. Haven't tried it extensively yet, but this is exactly what I was looking for. I'm tired of having to open a separate application just to view a word doc. This should be built into the browser just like pdfs are. The right click menu of this extension means you still have the option to download the doc if you want to and if one viewer isn't correctly displaying the document, it gives you other options to choose from. As far as I'm aware, this is the only firefox doc viewing extension that has this functionality. Will update this review if I run into any problems.