[notifications] can we make the volume notification bubble less intrusive

I agree. This will be addressed in the new notification system design. Those use cases such as volume control and brightness, battery charging, progress feedback, etc., will have a different layout and usage than the 'normal' notification bubbles. They should be more subtle as their true nature is to provide feedback and remove uncertainty about background or implicit operations the system is performing.

They should not be persistent or stack, as they are above other elements on screen, user should be able to tap through them as the current activity remains visible and interactive. The idea is to make them as unobtrusive as possible, while still showing the user useful information.

The standard duration/timeout is yet to be discussed. In the NotifyOSD wiki, the standard duration for a confirmation bubble is 2000ms, can anyone confirm this is correct for the current built?

I'll add further information on this subject from next week.

Just for info when i modify the volume the notification bubble stay up for 4 sec after manipulation.
I did suggest to put this kind of notification in the top header bar of the dash like the "tap to return to call" notification of the dialer app.

Screenshot of tap to return notification

- Design comment -
  01/05/2015

There are new design for UX and visuals for volume notifications "Notification system" ( page 43 )
https://docs.google.com/document/d/1xDSZ_dnAMAlhgFnnyjJEibaITXjVLp1_pnj_tATNm9I/edit#

You can now swipe the volume bubble away (at least in RC-propsed) so its not intrusive (at least in my opinion)