DeathKnight impressions

This weekend i spend some time trying out the Deathknight, firstly i did the complete questchain untill you get out of the instanced zone and enter the actuall world and after that i played around with the other two specs.
Can't say it's much more then a first impression as i ended as a level 57 with many new skills short aswell as a few points to try to top tier talent, still it gave me a good impression of the playstyle and the quests of its current state... but you never know what Blizz is still going to change right?

Quests
The questchain will explain you how you become a "man" of free choice in a series of quests in which you will meet quite a few know lore characters like Mograine, The Lich King himself but also the Baron from Stratholme. The quests themselves are quite versatile, still there are a few "kill X stuff" quests around but with the majority they have tried to offer something new or at least fun.
What also impressed me was that you play in instanced versions of the starting zone, depending on your progress in the questchain. If you have set up a cauldron in a quest it will actually be there from that point on, destroyed stuff will remain destroyed...really adds to the feel that what you did effected the world. I really hope they use this method of story progress more often.
The only downside is that when you finally finish your Deathknight quests after a final epic battle you are left in Eastern Plaguelands, stuck with doing what i've always considered some of the worse quests in Azeroth. Luckily 1 level is easily done and after that you can enter the Outlands on level 58.

Blood
Considered the DPS spec and this is what i used to level at first. It offers quite some damage aswell as offer some healing abilities to yourself and your group. At higher level you get some more area abilities and ofcourse you can put some points in either the Frost of the Unholy. The top tier talent in Blood is a flying sword which mimicks your attacks as long as you have runic power which is basicly your rage. It won't double your dps as you won't be able to use runic power at that point for your own attacks but there are still the skills that require runes which you can use.
Without much doubt this will be the best PVE spec in raids aswell as re-assure smooth and fast leveling.

Frost
This is considered the Tank build with more magic/physical damage reduction in it (some in the other trees aswell so going a bit into Blood should be required). What i noticed with this spec sofar is the somewhat more limited options then with Blood or Unholy, this will give tanks some more freedom to watch surroundings i guess so that helps.
But don't set it aside for just tanking, i skipped most of the tank talents and i quickly noticed the ammount of control you would get with this spec.. almost as if you are a frostmage but with armor and a kickass sword. With the freezing and slowing talents it's quite possible to kite some harder mobs to death, i've tried it on a couple of mobs and although i didn't spec in slowing mobs with my frost spells it was quite hard of them to even lay a finger on me.
It somewhat depends on some proccing luck ofcourse.
When doing mobs one on one the Bloodspec will be slightly faster but if you plan to tank later on with your deathknight, do give Frost a try with leveling.

Unholy
I'd like to call this the Fun spec myself. When speccing into this you lower you CD on Ghoul summoning aswell as lengthen the duration. It also adds a petbar so you have more control over your pet aswell as have some extra skills, without this talent the Ghoul will just do as he pleases which can be quite annoying. People say this is the PvP spec and i did see quite a few potential skills for that, but if you would choose this spec for leveling you are in for quite a few smiles on your face... exploding corpses, leaping and selfdestruction Ghouls.. what more do i need to say.
I could easily take on a group of 4-5 with this spec and come out with half my health.
The other specs will have more AE abilities aswell on higher level but they won't have exploding corpses which is an absolute blast.
This spec offered the most options so far and has the smallest chance to turn into couple button bashing gameplay.

Conclusion
Bloodspec should be your choice if you want to perform at your best in a PVE raid as DPS, Frost would be the spec to go if you love tanking in either 5mans or raids and Unholy is your spec if you either PvP or mostly solo.
However... each spec has some talents which would be worthwhile having one of that spec in a raid, mostly in the form of party healing or resistances.
Also, some builds complement each other.. having more then one deathknight in your raid will boost each others potential. The Blood dps spec becomes alot better when bringing an Unholy DK along for example.
If you want my oppinion; I'd likely level as Unholy as it seemed the most fun in the small time i played. However if you plan your DK to be your main, do level with the spec that will be your final spec as much as possible because each tree has quite different playstyles and the experience will help you at 80.