So, I'm finally starting to figure out this whole "Death Knight" play style thing. It's a little crazy. See, I've played classes that had Rage or Energy bars. You want to use that up as quickly as it regenerates, and it regenerates fast. I've played classes that had Mana bars - you want to ration out your mana, and usually need to drink to fill it back up.
The Death Knight has neither. Instead, they have a Runic Power bar and 6 Runes; 2 each of Blood, Frost, and Unholy. Abilities require the use of either Runes, Runic Power, or - neither? Yeah, some abilities require neither. Runes slowly replenish themselves as used. Runic Power is generated by using abilities.
For instance, my DK has all 6 Runes available and no RP generated. I use my Plague Strike ability (instant melee ability, it also applies a dot), consuming 1 each Blood and Unholy runes and generating 10 RP. If I use my Blood Strike ability (instant melee, but real damage relies on the target being diseased) I consume 1 Blood rune and generate only 1 RP. White damage melee attacks do not appear to generate any RP.
Conversely, some abilities USE the Runic Power, instead of generating it. Blood Boil, for instance. Now, you can see from some of the skills, spells, and abilities linked that DK dps is an intricate choreography, combing Rune-using, Runic Power-generating, diseasing, and the abilities that base their damage on diseases already on the mob. And this is just the dps! There are also all those diseasing / summoning-ghouls-thingies in the Unholy tree, and then there's the whole slew of "tanking" abilities.
Here are my concerns:
A) Although Blizz does a great job of introducing newborn DK's into the world, the 3 talent trees offer so many spec-specific abilities. Level out of the starting zone as Unholy, and then you have no clue how to play while specced Blood.
B) I've thought from the beginning that the best way to learn a class is to level it from 1 - it's much more difficult to be handed a whole pile of skills and try to figure out how they work. DK skills play off of each other in large part which, while uber-cool, complicates matters further.
C) I've got my safety goggles (and helmet - just in case) all polished up for when they roll out the math behind Runic Power generation. Anticipating this, my friends, gets my geek on.