The only slight issue I've found with it is the Earth View doesn't display when you open a new instance of Firefox (i.e. a new window, or starting it up for the first time).
A workaround I've found to get this to work was to open the following two tabs: - about:preferences#home - an empty new tab
From the about:preferences#home tab, click "Use Current Pages" under the "Homepage and new windows" section. From then on, opening new Firefox windows will also display the Earth View extenstion!
