Plot: the plot of the movie is relatively straightforward, and follows the same basic premise as the manga: Yagami Light finds a "Death Note" dropped by Ryuk, a shinigami (god of death) and decides to use it to purge the world of criminals. Subsequently, the police and mysterious detective L begin to track him down. However, it doesn't really get very far despite its length (over two hours) because it bulks itself out with an original plot thread - in fact, the movie only gets as far as Light and L meeting for the first time.
Plot Changes: Chronologically, it's much the same as the manga - but a massive plot alteration comes in the form of original character Shiori. I'm still not entirely sure why they chose to give Light a girlfriend - but she has a major role (along with Naomi, who now has a much bigger role than in the manga) - and an event involving her, Naomi and Light is the climax of the movie.
Misa has a very minor role, although given how little of the manga timeline was covered, it's not really surprising. She only has a couple of scenes, but it's nice to see her. Rem makes no appearance.
I was a little disappointed that they changed one of my favourite scenes - I won't say how in case you haven't read the manga, but Light and L meet in a completely different way. :( There were also a number of weird, irrelevant-seeming changes, as you always get with movie adaptations. :p Such as changing Raye Pember's surname to 'Iwatari', and altering the NPA Kira team to include a woman. Unimportant, but odd to note. :p Acting: On the whole, I think the acting was excellent, and the movie was (mostly) cast brilliantly. Although I still don't think that, visually, Fujiwara makes a very good Light, he was certainly convincing, and does a good evil smirk. :p I think most of the problems I had with Light were down to direction, rather than Fujiwara's acting. (Also, I think it has to be said he does a great job with Ryuk - you can't tell he was acting with a stick at all :p) Personally, I think that Matsuyama really stood out as being plain awesome. :D His L was nigh-on-perfect, and I don't even mean in appearance; the gestures, posture, the way he holds things and his mannerisms in general. Slightly more sullen than I'd expected, but brilliant. (and his love for sweets is still there, and even more emphasised than in the manga. I think he's eating in every scene. xD) Also notable was Seto Asaka - I just think she played Naomi really well, especially within the new role given to the character.
CG: (ie, Ryuk!) :D Ryuk was certainly... interesting. But he's one of my favourite characters in the manga, and I loved what they did with him. His voice is perfect, and appearance-wise, pretty much got him just right. Only problem is, sometimes the CG just doesn't look that good. It varies of course - sometimes it looks amazing, but other times... really not. But on the whole he was done well, considering how surreal his appearance is.
Pacing: The movie has a really interesting opening - you see a hand writing in a book, and then various criminals dying of heart attacks, while their name is 'written' across the screen. Unfortunately, after than I found it a little slow until L showed up (which wasn't until after halfway through) - although perhaps that's due to him being my favourite character. But regardless, since a lot of the movie is just setting things up and exposition for later, it was probably to be expected. That's not to say it isn't interesting, as it is, but... one of the best aspects of Death Note is the interaction between Light and L, and you don't get that until later.
Overall/General: I think it's a great movie, and works with the premise of the manga well, without being slavishly faithful (which is never a good thing :p) However, it does have its problems.
Personally, I wasn't that happy with Shiori's addition to the story. Taken by itself, her plot-thread was actually rather interesting, and a nice idea. However, I felt it altered Light's character too much - his motivations for doing what he does; what he's like as a person. They already changed him by leaving out that part of why he does what he does is because he's bored (Ryuk, too) - and, add Shiori, and you're left with a cold, evil teenager who hates criminals, and apparently seems like he can get close to people. In the movie, I almost think he comes across as too cold-blooded, too soon.
This is all fine if you haven't read the manga, I think, and it's probably brilliant if you can take it for what it is. But... I missed Light's boredom and utter god-complex which was so obvious in the manga. :p And his aloofness - the implication that he wouldn't have a girlfriend because no-one was good enough for him.
Er, but my slight issues with Light's character aside, it's a great movie. xD dark and full of suspense (but with moments of humour... L offering a kebab of sweets and cakes to Chief Yagami in total seriousness comes to mind :D), and very enjoyable. I can't wait for the second half, and I'm really interested to know how they're going to try and resolve it (as, clearly, Death Note actually goes on for five more volumes after where they're intending to stop.) So, despite a few issues... Death Note pt. 1 = awesome. :D
