Enable the 'Do this automatically for files like this from now on' option for it, and the extension won't bother you with double download dialogs. You will notice it has a link next to it that says 'application/prs.oib-ask-once', click on it and you will see a download dialog pop-up. Enable the setting that reads 'Never ask to confirm 'Save File' action'. There is a fix for this as well: head to the about:addons page, click on Open In Browser > Options. There is a caveat, you will see the download dialog twice anytime you try to download something (EXEs, ZIPs, MSIs etc) when you have the extension installed. Other file types will be downloaded as they're normally handled by the browser. Obviously, you will need compatible content as well for this to work. This is of course limited to the browser's capabilities. The extension also allows you to select the way the download should be handled it can be used to open web files in five ways: As a text, a web page, an XML, an image or a PDF.
