The fine folk over at DeathKnight.info have posted a video of the unique Death Knight voices we've all been promised. They don't have an entirely new set of voice emotes (at least not yet), they took a slightly different route. There's actually a sound filter over the voices, making them sound echoey and spooky. The females have been described as sounding like banshees, which is pretty accurate I think. If you're not a fan of the voice effects, you're allowed to turn them off in your Sound control panel so you won't have to hear it. Other people still will, unless they do the same.
I'm definitely a fan of this for most of the race/gender combos. Some of them are lackluster (in my opinion) such as the Female Dwarves. The best? Male Blood Elf by far. That laugh? Awesome. Just awesome. I'm sure we'll see a couple of tweaks to this before the end of the beta period, but they're definitely on the right track, I think.