I'm going to say that you don't need a spoiler warning on this one.
Normally, I don't really like going to see things when they open, the same time as a huge, swirling mass of people. People, especially in large groups and in movie theaters, can tend to be selfish, rude, noisy and annoying. And I just hate that. Tonight, however, I saw the 12:01 of The Dark Knight with a building full of a few hundred Batman movie fans. That's a different crowd. Sorority chix with homemade "The Batmobile is How I Roll" T-shirts. Guys painted up like the Joker. People with bat cowls and pajama capes, parading around without a hint of apparent self-consciousness or irony. The tiny Indian woman sitting next to me who's wrestling with some inner demons, I think, based on her reactions to Heath Ledger's Joker. Amazing. I found myself blissfully entertained by a patchwork community of fandom. Awesome.
I am given to describe Batman Begins as a great movie which has a superhero in it. This movie is equally great, and has the same superhero in it. If you liked the first one, you will like this one, which exceeds the first in many ways. The stakes are higher, the performances, especially on the parts of Bale, Ledger, and Oldman, are strong. Bale actually plays three people, if you're paying attention: Wayne as he is, Wayne's public face, and Batman. He juggles them all quite well - and his vocal and physical cadence as Batman would terrify a normal person. Much has been, and will be made of Mr. Ledger's unfortunately final performance, so I will say only this, and you can give it what weight you feel it deserves: When the Joker is finished speaking, you as a viewer exhale. He's that good. Heath Ledger is my Joker, apologies to Jack and Cesar. Oldman as Gordon is brilliant, and played like is in Year One, which can only be a good thing. Everyone is good, Eckhart's Harvey Dent is great, Maggie's a big improvement over Katie Scientology, and Caine and Freeman are playing these roles effortlessly now, while bringing more depth to both them, one with some history, the other with a principled stand. It just comes together perfectly.
(One small note: If you've spent a lot of time in Chicago, the cityscape can be a little distracting in places, 'cause you really recognize it, but proper homages are paid, right down to the similarity of the Gotham license plates to those of the Land of Lincoln. Gotta get / make me one of those Gotham plates.)
This is a riveting movie, so I highly recommend you go see it. It is different. It is less cerebral (sort of), less inner-directed. It takes more risks, but nothing that doesn't serve the narrative. It's disturbing and evocative, and if you let it, will make you examine ideas about societal mores and culture and basic principles of right and wrong and what those words & concepts mean, whether you believe they are ironclad or somewhat flexible. Superheroes have, as a direct ancestor, mythologies and morality plays, so this, after all, is part of what a movie like this arguably should be doing. It does it very, very well. I particularly liked the bit with the boats.
There are little visual cues referencing a lot of previous material, everything from the comics (specifically this painting, Killing Joke and Dark Knight Returns) to the 1989 movie, but if you don't catch them, it won't matter. Nolan and Goyer (who we all know's a fanboy anyway) and company are doing Batman the way he should be done, and avoiding the campy stuff completely. Batman Returns, with it's similar publicity and three villains, was the beginning of the slide for the first series, while this movie takes three villains or more, depending on how you count, and turns it into a major strength.
You were going to go see this anyway, and I'm saying to you - trust your gut.