Death Knights in Cataclysm: what will change?

Well, we've finally gotten the big talent tree revamp we've all been waiting for.  It's obvious that the Death Knight trees are far from finished, but we are starting to see themes forming, and getting some idea of what will change.  A lot remains to be implemented and seen, so it's hard to judge these too deeply.

Overall:

• New rune cooldown system: this one was announced a while ago.  Simply put, runes of each color refresh one at a time.  You essentially get half as many runes during ongoing fighting, but if you are inactive for a bit you can start out with all 6.  Each of the 3 colors is basically its own energy bar.  The damage and runic power generation of the abilities and talents has been doubled across the board to compensate.  In theory, you should have more free GCDs since waiting a second to use a rune won't lead to a large dps loss down the road as future recharges are delayed.
• Runic Empowerment: Until recently this was a first-tire frost talent, but is now baseline for all DKs.  When you use a runic power ability like Frost Strike or Death Coil, you have a 45% chance of refreshing a random rune. That's a lot of free runes.  This adds an element of randomness to all rotations.  I'm worried that it will undercut the new rune cooldown system because you'll feel pressured to always have at least one full rune of each color on cooldown in case this procs.
• Each spec gets its version of death runes right off the bat, as well as a key ability (heart strike, frost strike, perma-ghoul).
• Anti-magic shell no longer generates runic power off of damage by default.  This does remove a measure of skill from the class (timing AMS to optimize free RP), but hopefully new abilities will make up for it.

Blood:

• Now a pure tanking tree, and the only tanking option.  Our own Prot tree!
• Blood presence is now the tanking presence, having the same effect as the current frost presence
• We just pile on the cooldowns: IBF, AMS, Vampiric Blood, Bone Shield, Rune Tap, and Will of the Necropolis all in one tree!  Also, WoN now procs a free Rune Tap heal and refreshes the ability's cooldown, adding an active element to save yourself when low on health.  We clearly have more cooldowns than other classes, and it will be very interesting to see how hard this is to balance.
• Block equivalent: in Wrath, Death Knights have been at a disadvantage for smaller-scale fights because of a lack of a block-style mechanic (druids can proc a mini-shield on crits).  There was mention of a block equivalent a while back, where we would have a chance to auto-heal for a percentage of the damage we take.  That appears to have been scrapped, as it does not appear in the current talent trees.  I still hope it makes a comeback.
• Innate crit immunity: say goodbye to defense rating, the most annoying stat ever in the game!  It was confusing and served as an unecessarily stark barrier-to-entry, and required too much outside research to even begin to understand.  Good riddance.  Now we get PvE crit immunity from Blood talents, just like other tank specs.  Hurrah!
• Attack Power Debuff: just like with Block, DKs were the only tanking class with no attack power debuff they could apply to enemies (Demoralizing Shout, etc.).  That's finally changing, as talents in the new blood tree give Blood Boil the ability to apply that debuff, making it into a damaging Demo Shout.  Another great call by Blizzard, it's a necessary tanking tool that we went without for too long.
• Dancing Rune Weapon: now you can parry for two!  In a great leap in the realm of MAKING SENSE, having a second weapon flying around in front of you gives you a sizeble bonus to your chance to parry.  But wait . . . is that another tanking cooldown?  OK, guys, this is getting a bit ridiculous.  6 cooldowns?  That's a lot of runes and runic power being devoted to survivability (even though IBF can be talented to be free!).  Hopefully that won't cripple our threat.
• Sub-specs can only go 10 points into another tree at most.  This leaves you with very few attractive talents currently within reach for tanking.  You're basically picking between a reduced DnD cooldown and a fear immunity. 

 Frost:

• With blood presence taking over tanking duties, frost presence now boosts damage and runic power generation (sorry, no more self-healing)
• Pillar of HOLY SHIT (aka Pillar of Frost): I'll just link the tooltip for you:"Calls upon the power of Frost to increase the Death Knight's Strength by 20%.  Icy crystals hang heavy upon the Death Knight's body, providing immunity against external movement such as knockbacks.  Lasts 20 sec."   Notice anything . . . missing?  Like, say a cooldown?!?  It used to be at 1 minute, maybe wowhead isn't displaying it.  33% uptime is still pretty good - but where will we get the spare frost rune?
• You can now choose between a dual-wield talent and a 2-hander talent.  This is quite a relief, as I'd love to have a 2-hander spec without a pet.
• Frost DKs now get the 4% increased damage debuff for raids that was previously limited to combat rogues and arms warriors.
• On a Pale Horse was moved to early Frost.  I find myself constantly wishing I could fit this mount-speed talent into my builds on live.  I hope Blizzard follows through on the promise to leave you  points for optional talents so I can pick this up.
• The top tiers of unholy have little worth subspeccing into, so you'll end up putting the majority of your extra points in blood in the current build.  

Unholy:

• The biggest change to unholy is the loss of Bone Shield.  Most players underestimate this talent's current impact in raids.  Taking 20% less damage at all times is huge.  It prevents some insta-gibs (hello Mauradin cleaving me as I run past him on heroic gunship), reduces healer panic from big aoes, and makes you all-around the most survivable dps in any raid.  Get lucky enough to be the first Mark on heroic Saurfang and laugh all the way to your purples.  This would be even more important in the new Cataclsym healing environment, so it was placed 11 points into the blood tree to prevent non-tanks from getting it.
• The damage buff Hysteria was removed from Blood and replaced with a similar cooldown called Unholy Frenzy in the blood tree.  Sudden Doom also got moved from blood to give unholy free death coil procs.
• Ghoul Frenzy keeps getting buffed in the beta builds.  It's more afforable with the new talent philosophy, but it remains to be seen if 1 unholy rune will ever be worth it, especially now that:
• Scourge Strike costs 1 unholy rune, instead of 1 frost + 1 unholy.  Obliterate and Death Strike, the other FU abilities, remain unchanged.  Blizzard will presumably be introducing some use for the extra frost runes, as they can't possibly expect us to just cast extra Icy Touches, especially given the ludicrously long disease durations we get from epidemic.
• The likely solution to the frost rune problem is the new Festering Strike, which further extends disease durations and is the first 1 Blood + 1 Frost ability.  I don't see the other trees getting use out of this when they could cast Obliterate or Heart Strike.

Problems:
These builds are clearly still early and in flux.  Some of the priority things for Blizz to work on:

• Top-tier talents are lackluster in Frost and Unholy, especially for sub-speccing.  At least Improved Icy Touch, Icy Reach, and Vicious Strikes should be both reworked and shuffled.
• Ghoul Frenzy should either have its rune cost removed, or be reworked to be a desirable cooldown.  Maybe reduce it's duration to 30 seconds, double it's damage effect, and give it a 2 minute cooldown.
• Frost needs its "required" dps talents to be reduced in number.  Dual-wielders can only afford 1 optional utility point, while 2-hander-wielders can technically afford 4, but are forced to put two of those into Icy Reach and the other 2 into tier 2.  The whole tree really needs rearrange-in'.
• Can you tone down the cooldowns in Blood just a little bit?  And are you sure threat won't be an issue with all those resources going to staying alive?
• Festering Strike will have to be implemented very carefully.  Not only will it have to do more damage than an Icy Touch + Scourge Strike (remember, unholy gets Reaping automatically, so blood runes become death runes after being used for blood strikes), but it will also need a way to deal with the fact that you aren't going to be using the blood rune for a blood strike, and thus won't be getting a death rune later.  In the same patch, Festering Strike was added to Reaping, meaning that the Unholy rotation currently looks like SS > SS > FS > FS > SSx6 or something (I'm not really accounting for the new rune recharge mechanics there because I haven't tried them).

Any further evaluation will have to wait until I can actually get into beta and find out the real consequences of the new talents, the new rune cooldown system, and haste's effect on rune refresh speeds.