Well Harvey Dent is actually probably my favorite character of Batman's rogue gallery. Joker is my favorite villain (like most) and is by far the most entertaining. But the one I really like seeing explored and to get in the psyche of is Two-Face. Joker is better as an enigma, a mystery. Harvey Dent's tragedy is we know who he is and where he came from to end up at such a low and dispcable point. Also, it shows Batman as a far different hero than most. While most would not give up on their friend, no matter how far he fell (Superman wouldn't, Spidey didn't when Harry went crazy or everytime Conners turned into the Lizard) in the comics Batman literally turns his back on his friend by the end of Dark Victory and considers all the good Harvey Dent did absolved and looks at him not as a fallen friend...but as a villain to deal with and nothing more. That is a striking relationship that adds some poignancy and tragedy to Batman's character as well.
So I am all for some Two-Face action. However, if they do this right, I'll be contented. I personally would like it to follow the unofficial Bat-origins trilogy (BB=Year One, TDK=Long Halloween and Batman 3 would=Dark Victory). But if Nolan has other plans I am fine with that. I love an auteur who is faithful to the source but is unafraid to stray from the details to create something new or in their unique vision.
As long as the rise and fall of Harvey Dent is well displayed and we get some good Two-Face action (I want to see a confrontation between him and Batman similar to the one they had in TLH over Falcone). I don't know how he dies as I refused to read the spoilers and only found out he kicks it on accident. But I always thought Two-Face was most interesting as a mirky shadow/reflection of Batman.
Here was the member of the justice trio of Bats, Gordon and Dent. Dent was closer to Batman's philosophy on getting things done than Gordon's by-the-book approach. He even helped Batman do illegal things to weaken the mafia's hold on Gotham. But he is a vain and ambitious man (his two flaws). These are both directly attacked when his life, marriage are ruined by the scarring of his face. He is pushed over the edge and does what Batman will not--he kills the bad guys so they don't come back. He is out for blood. He is still after the same ends as Batman but they are now enemies because Two-Face is a killer. Substitute a marriage to Rachel Dawes (who I think is pretty obviously going to get killed off by the Joker, but I'm just guessing) and you have a real tragic figure of a man pushed too far.
And that was the most interesting thing about Two-Face. He just took it further and further in Dark Victory to the point that Batman didn't even recognize Dent in the villain anymore.
And then he is "killed" by the Joker (I don't know if that is how it happens in the movie, but I hope it is something more cinematic). In some ways I wish in the new continuity that Two-Face stayed dead after Joker shot him off the cliff. Simply put, he was better as this tragic shadow of Batman than a mobster. The brilliant reinvention of Dent by Loeb/Sale never felt right to me when he becomes a villain in later years. This Harvey Dent (who is going to be the main inspiration for TDK's incarnation of him I bet) becoming a mobster. The things he felt stole his life from him and ruined his city...the things he wanted to destroy no matter if he worked with the freaks or not...never made a whole lot of sense.
So, if they kill him at the climax of his bloody retribution, I am fine with that. I would have rather it gone further and got more nasty between him and Batman in a third movie like it did in Dark Victory. But if Nolan wants to tell it all in one movie with new ideas for a third, I'm fine with that.
P.S. Don't tell me the circumstances of his death, I want to at least be surprised by that.