I've seen people do well with DW, frost, and blood specs. But I havn't seen any of those do the BEST dps. Unholy makes every other spec look like they just hit 80 yesterday. I've concluded that every spec can be good in PvE DPS, but it's the skill of the player that makes or breaks their "top dps" title.
Zeil you should post the armory to your toon.
This is my DK, and with my current spec no other death knight has even come close to me on meters, and I've been #1 for damage in this past week's raids. Our guild has cleared all content except OS - 3 Drakes.
The World of Warcraft Armory
I'm also ranked 23rd on my server for gear, and first for death knight.
Just go to the Realm tab and search US - Lightninghoof.
WoW Heroes - World of Warcraft PvE character info & ratings
I can post the WWS too if you want from last night's H-OS 2 Drakes up with me on top of the meters.
Even after the next patch, I don't see unholy getting nerfed hard enough to be worse than the other specs PvE wise. Unholy, Unholy, Unholy.