This isn't meant to be a be-all end-all of the state of DPS DKs in 3.3, just a mention of a few topics that have been floating around on EJ and in my guild forums.
1. Blood vs Unholy for DPS. Note that I didn't mention frost. That's because frost still sucks as we can see in this thread at EJ. If you look at the tables compiled by Shrakz (a poster), you can see how DKs stack up by spec, but also against other melee classes. Somewhat ironically given our facerolling reputation, we're in the bottom half of the group, but it seems Blizzard has done a pretty good job of balancing overall.
Anyway, if you've read my blog for a while, you may recall I predicted blood would eventually overtake unhholy for single target dps. It's getting very close now. I'd bet when we see enough guilds with 2-4 pieces of 277 tier pieces blood will start to creep ahead. For single target low movement fights, blood should end up as king. For aoe and movement fights, however, unholy is likely to still come out ahead, and both provide very useful buffs. Take your pick.
The jury's still out on my other prediction that dual wield will become viable again towards the end of Icecrown.
2. Gargoyle is bugged. There has long been some odd behavior on the part of our favorite winged pet. More recently, however, the poor guy has developed the bad habit of staying close to the boss when summoned and meleeing, which is a big dps loss. It seems the gargoyle flies straight ahead of you when summoned. If the boss is there, it melees. So, remember to turn 90-180 degrees away from the boss before summoning - this should allow the gargoyle to fly away from the boss, turn, and start casting for crispy fried awesomeness. Hopefully Blizz fixes this soon.
3. Should we use Unholy Presence (UHP) on movement fights? This comes up every time a new boss with heavy movement requirements is released. The logic goes that more time on target = more dps. However, it's becoming more and more clear to me that the answer remains in every case: NO NO NO!!!! Don't do it! Blood and Unholy dps specs currently don't suffer from being gcd bound, so the rune cooldown decrease isn't helpful. Time on target is not increased by much even on high movement fights, and if you're really desperate you can either enchant speed to boots or take the talent improved unholy presence.
How do we compensate for any excessive dps losses on movement fights?
a) good positioning. In my guild, we tank Putricide right there volatile ooze spawns so we can immediately dps it down. In addition, we're tanking most of the adds at the top of the key on Valithria - less movement (only need to run to suppressors). Lich King movement is minimal when the Lich King is kited properly during phase changes, and Valkyr should be properly slowed.
b) proper anticipation and crisp target switching. I do well on Putri in part because I've noticed I'm often the first person on oozes, and know when to break off and run back to Putri, and use little tricks like position myself to be knocked back towards Putri by the volatile ooze just before it dies.