Very good advice, I hope some devs here take it.
One other point: music volume.
You don't need to set the default to "let's rattle the walls of the room next to the player", some people still have decent hearing...
Oh yes, excellent point! I usually set music volume to 0.4 and sound volume to 0.7 as the default for my games, and so far I haven't gotten any complaints on it.
