Installing the extension this way works for me. The extension is well installed but not activated. Users have to go in Extensions panel to activate it.
I've just noticed the Internet connection is needed to see the extension installed. I need a proxy to have Internet access and when it's not configured the extension is not visible.
I still have a problem and maybe you have already faced with it : the default download folder and the homepage can't be configured under master_preference file anymore. Do you experienced it ?