Jadefury, also known as Leiah, writer of the World of Feedback blog, has fast become one of the most recognizable names in Deathknighting of those following the Wrath Beta. Among his contributions have been 2 videos that showcase the leveling playstyle of Unholy and Blood trees. They're definitely worth a watch for anyone who's seriously thinking of playing a Death Knight in Wrath of the Lich King.
The Unholy video, shown above, uses this spec. It actually relies quite heavily on two Blood talents: Butchery and Vendetta. Those 2 talents provide the Death Knight with health and runic power after every mob death, which helps power Corpse Explosions and allows the Death Knight to stand up to lots of monsters at once. Jadefury also shows the power of Death and Decay, Lichborne, and Bone Armor, and even throws in an exploding Ghoul or two, following it all up with a showcase of the awesome Death Gate animation.
I have to admit that I have some concern that this style of AE farming won't be viable for Death Knights everywhere, since in this video, he relied extensively on getting Runic Power via Vendetta due to quick kills on the low HP slimes in the Pools of Aggonar. On the other hand, it looks like a lot of fun, and solidifies my personal resolve to try an Unholy build first.
After the break, we'll watch the Blood video.
The Blood video is a rampage through Andorhal that showcases the brutal damage and lack of downtime that speccing deep into the Blood tree can provide. It's only a level 57 build too, so it has plenty of room to grow. It showcases the power of the life-stealing blood worms created with Infested Corpse, combined once again with the healing power of Butchery and Vendetta, which look like they'll be practically required for any good leveling or grinding build.
They're both awesome videos that give a good taste of what playing a Death Knight is currently like. Certainly, Death Knights can still change drastically in the future as they're polished before they go live with the expansion, but for now, they at least look like a fun class to level and have multiple unique and versatile options for DPSing.
Edit: Video embeds changed over to Filefront. Vimeo seems to be having trouble. Sorry, folks. -Alex