Not supported in FF, not supported in IE and two competing specs.<p>I'd say, no, it's <i>not</i> time to integrate web notifications.<p>Especially if you want a consistent user experience across browsers.<p>Nice informative writeup on the current state though.
Although I never saw gmail has the popup notification, but I really hope when I closed the browser, it somehow still will popup the notification, that will be super crazy.<p>I am not sure if OSX support web server push notification to the "Notification center" because, iOS is doing so.