Went to see the update and was blown away, literally!  Amazing music and pyrotechnics, all for free.  Advice: the best place to see the show is on the strip, right near the volcano, if you can see the valet car port for the Mirage from where you are standing then in you're in the right place.  Also DO NOT rely on the Mirage website for a schedule, it's always wrong, call in advance as sometimes it starts late (8pm), and sometimes ends early (11pm).