I've been waiting for this since Blizzcon '08 where they first tossed out the suggestion.
...
I'm still waiting on it ._. It was somewhat of a relief reading Ghostcrawler mention that they're still looking forward to implementing it, but I'm dying to read a bit more details about it. But then again, with Arthas and his defile... I don't expect to see it any time soon *shakes angry fist*