Gotta love it when other people do the work for you, right? Geistig over at Skeleton Jack has a great post on leveling Unholy, for those of you who like the idea of ridin’ around with your best ghoul by your side, being nigh unkillable in an entirely different way, and – oh yeah – moving really fast. Trust the lady, read the post, try the spec if you’re still comin’ up in the world. 
She mentions it briefly, but I can’t emphasize it enough – if you’re leveling Unholy, take On a Pale Horse. Frankly, I still miss the mounted movement buff today, given the sheer size of Northrend.
Stop used to be a warlock, then he was a death knight; first he was Horde, then he was Alliance again, and now he's Horde again. For good this time. Lok'tar ogar! 
Hey thanks! Yeah I specced ‘On A Pale Horse’ went against an elite with stun and was able to get back to bashing pretty fast. When I unspecced the talent and went back, I almost didn’t make it. So yeah out running your friends is cool, but getting out of a stun faster means getting back to the fight faster. Even as Undead ‘Will of the Forsaken’ only goes so far.
Geistigs last blog post..Death Knight Leveling: Unholy Specs, or “How to be an Unholy Terror”
I was unholy until about 73 then I went diseaseless blood… I never turned back