Let me preface this by saying that, of the Twilight book series, I have only read New Moon and Eclipse. I've also seen the Twilight movie, which is what most of this entry will be based off of.
Bleargh. I actually really like Robert Pattinson's acting in this one. I think he portrayed did a wonderful job of portraying Edward Cullen as being exactly as fucked in the head as he ought to be. Kirsten Stewart does a good job of being awkward as Bella, but honestly, her character is JUST as flat and boring as she was in the book. I'm inclined to avoid blaming her for it, though, because I'm not sure how much more interesting Bella could be made.
The way I interpret Bella and Edward's relationship now is that of a depressed, lonely, socially awkward, somewhat parentified teenage girl with an angry, depressive, lonely, socially awkward teenage boy who absolutely despises himself as a result of his vampirism. Edward, I think, is almost the stereotype of an uptight, fundamentalist Protestant, punishing himself constantly for his own perceived sins. You know, I could totally see him as an enthusiastic Calvinist, believing wholeheartedly that he is one of those predestined for salvation. But his mother asked Carlisle to turn him anyway; I could also see him almost being happy on his deathbed, expecting heaven, only to wake up and find out that he's become one of the "damned", so to speak. It'd be a good explanation for his angst, at any rate. :P Then, I think his actions are affected by his self-perception as well: He believes that he is damned and unredeemable, so in a kind of self-fulfilling prophecy, he acts like a bit of a douche to the people around him.
At the same time, however, the heightened abilities that come along with being a vampire have given him an unusually high level of self confidence. He's grown used to being around people who are far, far below him in levels of skill, so he looks down on them, but he also views himself as one of the damned, so he hates himself at the same time.
Man, this is almost too fun.
Bella and Edward's relationship is unhealthily codependent. As several people have pointed out, Bella seems to take care of her parents a lot, and she's very isolated from other people outside of Edward and later on, Jacob. The way she's portrayed in the movie only serves to augment my impression that she's quite socially awkward. She wants love, and I'll bet she also wants to be protected, and Edward gives that to her. As for Edward, he is initially forced to pay attention to her because of her unusual scent, and he is fascinated by her because she's the first person whose thoughts he's ever been unable to read; however, this progresses to something deeper when he admits his vampirism to Bella and she tells him that she doesn't care. His own attitude serves excellently to alienate most people, and his vampirism will work just fine to alienate any others- except Bella, who will stay madly in love with him no matter what he does. He loves her for this, but his own sense of vampiric superiority over humans keeps him from treating her respectfully. He believes that humans are infinitely fragile and delicate, and incapable of really understanding the dangers of the vampiric world. Thus, when he does the kinds of things that I always complain about, like kidnapping Bella in order to get her away from her werewolf friends, he thinks he's acting in her best interests. Bella herself is addicted to the feeling of being loved, and is probably flattered by what he does to protect her, not understanding the lack of respect it demonstrates.
In order for Bella and Edward's relationship to become a healthy one, they're both going to have to gain more self-esteem and get lives outside of each other. Edward's superiority issues are also going to have to be addressed. I actually think their relationship might be healthier if Bella were to become a vampire, because then Edward might stop seeing her so much as a weak, fragile flower in need of protection. I think the Edward in the movie might be taking steps towards this: He seems to be constantly nervous around Bella, which you could interpret as him constantly trying to keep himself from eating her, but it doesn't seem to be all that kind of nervousness. I think he's actually afraid of how she might judge him, making her perhaps the first human in a long time whose opinion he's given a damn about.
Still, he's got a long freaking way to go, assuming he ever does get there, and in the meantime... man. Let's just say I've spent an awful lot of time now analyzing a romance that I don't find very romantic.
Yeah, so maybe my character interpretations aren't canon. You know what? I don't care. I do what I want! [/Cartman impression]
...
Aside from that huge digression, I thought the movie was boring. The interactions were all dreadfully stilted, the chemistry between the leads almost nonexistent. That scene where Edward screams, "As if you could outrun me! As if you could fight me off! I'm designed to kill!" at Bella was interesting, although I've got to say, the special effects did not impress me. (Read: They were AWFUL.) Even the vampire sparkles were painfully half-assed. :( Oh, and all the Mac product placement was ridiculous. Sheesh.