I'm in the same boat as Matthew.  Just switched from a blackberry to GN ICS.  Overall I like it but it desperately needs this basic sound option.  The BB has the ability to create sound profiles you can setup to control phone, email, calendar notices, etc., as a simple selection.  The profiles have to be configured initially, but then it's easy.  When I go to bed I select my Bedtime profile.  It silences email alerts, sets the phone ringer to max, and sets the calendar event notice to max as I've slept through an early morning conference call once!  Don't make me sleep through another one!!