Really useful, however I am also having issues with it in the latest versions of Firefox. The context menu is there, but it doesn't search anything when clicked (no new tab with search results opens). The only way to "fix" it is to reinstall the addon, however it breaks again shortly after.
Edit: Also just noticed an incompatibility with X-notifier that checks emails. When this addon is enabled, the X-notifier does nothing when clicked. It starts working every time this addon is disabled.