It is very welldone, the pacing is nice, since it is almost the same as the manga (in actuality, a light novel) that has perfect pacing. It is very suspenseful and clever, with excellent use of cliffhangers. Is is a battle of wits between Light and L (and some others latter on), that really differs from your usual shounen. It is nice to say, too, that Light is totally and completely the villain, and an excellent, sadistic, maniacal, bad person villain. And yet he's the main character, our point of view in the anime, which is nice for a change.
Oh my God, it is awesome! Since the opening, till the ending, and it really heps set the mood and heighten the tensions and suspenseful atmosphere with excellence. I just don't like the second opening and endings. The dub is also really nice.
They are not very deep, and yet they have much flavor in them. The only character I particularly have a problem with is Misa Amane, she really does bring down the cast of the anime, she doesn't fit in.
Awesome. Takeshi Obata's art is very rich and sofisticated and translates well to the screen. It has many nice little touches here and there, with clever use of visual metaphors and little-to-none fanservice. It is also very cinematographic and intense.
In general, all of the aspects blend really well for a nice complete product.