I'm sure there are approximately a bazillion different situations in which this could come in handy, but what makes it extra appealing for the warrior is how it can be paired with mechanics that depend upon a minion receiving damage in order to reach their full potential. Got a berserker minion who gets +3 to attack after being hurt? Toss him Commanding Shout and you don't have to worry about him dying that round. Got your opponent's minions on the brink of death, but not sure you'll survive the next attack? Pair Rampage's +3/+3 with Commanding Shout and watch the other player squirm with impotent rage as you annihilate all their best-laid plans. What could possibly be more satisfying?
Check out WoW Insider's Hearthstone coverage for further information, and we all look forward to Hearthstone's release!