I stumbled on this add-on to Firefox today, finally solving an annoyance I’ve had for ages. Ubuntu Jaunty has a great new notification system (not perfect, but certainly a step in the right direction), yet Firefox continued to use its own silly notification in the lower left corner of the screen.
With this add-on the Firefox will utilise the notification system that comes with Ubuntu Jaunty:
Get the add-on here.
Update: So it seems this only works with the completed download notification. Hopefully the author will integrate it further into Firefox in the future.