The event is truly awesome, IMO. As someone who's never seen the opening of AQ event, having dozens of players in the same place fighting the same enemy is quite the show.
SPOILER ALERT!
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I liked how you get to "unlock" the druid class for trolls in cata by fighting an elite tiger and she reveals herself to be a troll. She aids Vol'Jin in the fight and promises she'll join his tribe. You get a cloak (no stats) and a little charm that transforms you into a troll for 30 mins.
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I've also uploaded my screenshots from the event; again, don't look if you're afraid of spoilers:
http://img830.imageshack.us/g/wowscr...810171153.jpg/