For starters, it's a guaranteed critical hit. You can have no critical strike rating at all, and you'll know that Dragon Roar is going to crit. This means that it's a dynamite AoE threat move if you want an ability you can save for emergencies instead of using on cooldown the way you will Shockwave.
In addition, Dragon Roar's damage is substantial, and it combines an AoE knockback with a full 5-second stun, making it very potent for PvP as well as for dealing with sudden adds or keeping adds under control longer. And while it has a 1-minute cooldown, making it longer than Shockwave, it's a full half-minute shorter than Bladestorm, meaning you can use it more often.
Also, it's bloody awesome to yell and see an expanding blast of damage flow out from you in all directions. It's hard to catch a good screenshot of that, though. Dragon Roar combines good damage with excellent short-term control, and I have a very hard time deciding between it and its rivals.
It's open warfare between Alliance and Horde in Mists of Pandaria, World of Warcraft's next expansion. Jump into five new levels with new talents and class mechanics, try the new monk class, and create a pandaren character to ally with either Horde or Alliance. Look for expansion basics in our Mists FAQ, or dig into our spring press event coverage for more details!