Spoilers and long review below!

The truth is that, 'Kimi ni Todoke' is not for everybody. For 'Kimi ni Todoke' (which I will now shorten as 'KnT' from now on) is all boils down to two factors:

1. How much sweetness can you take in a shoujo?, and 2) How much slow romance can you take in a shoujo?
   Because KnT's central point is that slow sweetness of high school romance, if you cannot take the "doki doki" or slow factor of shoujo, you will end up frustrated with KnT after a few volumes.

In my review, I have tried to remain as objective as possible.

Plot/Story
KnT's plot, to put it in short terms, follows the school life of the heroine Sawako. Sawako is a kind, gentle, shy spirit, but is very misunderstood by her classmates because of her appearances resembling "Sadako", a ghost from the horror movie "Ring". Thus, Sawako has no real friends and is lonely...Until the class popular boy, Kazehaya becomes her friend, opening the door for Sawako to make more true friends, and even learn about love...from whom? Kazehaya, of course.

Kimi ni Todoke is nothing stellar in its plot line. We've seen the popular boy likes unpopular girl storyline before. And its concept, while cute, is nothing fresh. Thus, while the sweetness of it is very appealing, the most I can give it is a 3.5 for its rather ordinary plot... Oh, don't throw stones at me yet, KnT fans! I haven't finished explaining... Wait for my next few sections of explanation.

Characters

Now, where is where we get to the good stuff of KnT.
While the plot is generic, where KnT gets to shine is in its focus on this idea of the sweetness of the slow, innocent high school romance. The characters, the development, and the emotions - everything is sweet, slow, and innocent.

First of all, the characters-
Sawako is simply put, one of the sweetest heroines ever. She is shy, gentle, and kind - she is the sweet and innocent girl. She's so sweet, where's to the point of sickening you - but you still can't come to hate her. You know how in real life, nobody hates the really nice kids? It must be like that - she's so sincerely sweet that it's difficult to hate her. The only reason you could dislike her is maybe her denseness. I mean, the woman is sweet and all, but can she not sense the major signals Kazehaya is sending her? Well, denseness is a requirement for the slow romance. And as I have stated before, if you do not like slow romance, KnT is not for you.

Kazehaya, our hero. Ah, my favorite. What I love about Kazehaya is that he is realistic. He is the class popular boy for a rather realistic reason: he's fun and easy to get along with! These days’ shoujos imply that the ridiculously good-looking rich boy is popular, even though he may be a snob. But no! There are no rich hot snobs in every school in real life. Most people are popular because people like them for their personality - which is exactly why Kazehaya is popular. Thank the author for the realistic male lead! Kazehaya is also one of the sweetest, cutest male leads ever. His love for Sawako is extremely innocent but sincere that it's difficult to not root him on...especially when Sawako's dense as dense gets. You end up cheering for the guy, really.

The side characters are all likable - Sawako's friends, Kazehaya's friend (I would like to add all of them, but I'm way too lazy to right for now) are all funny, but dependable - which is what friends should be like. And I even really liked Sawako's rival, Kurumi - she started out as the low, sneaky rival at first. But she turns out to be a caring, confident in the inside girl who actually sincerely likes Kazehaya.

The best part of all these characters? They develop! Sawako doesn't stay the shy dense girl forever, she slowly breaks out of her shy girl shell (very slowly, but it happens) while Kazehaya slowly builds up his courage to confess to Sawako. And as I stated before, even the rival develops! She goes from the dislikable, sneaky rival to this confident and caring in the inside girl.
In the character department, KnT wins a big fat 5.

Drawing Style

The drawing style is meant to make you go "Aw, how cute..." There's really no avoiding of that.
If you have said "Aw, they're blushing- look at how cute they are..." at least once during KnT, you know what I'm talking about. As I said, everything in KnT is that sweet innocence of high school romance. Even the drawing style is supposed to be cute and innocent. There's a lot of blushing, a lot of shy facial expressions, but in the end, it's all cute.

The drawing style is easy on the eyes - the author manages to get all the main characters looking different and while it's not a flashy style of drawing - it makes you feel all warm in the inside.

Enjoyment

As I have stated, everything in KnT is meant to be focused on a slow, innocent, sweet high school romance. That being said, KnT is slow. If you don't like slow progress, you will most likely not enjoy KnT. That's why the most I can give the enjoyment is a 4, considering the slow (maybe even painful) progress.

But as slow as KnT is, when we get to a point where Sawako and Kazehaya's romance develops, it is a really, really beautiful moment. You can't help but feeling that "Awww" coming up in you, your heart beats faster and it's that classic, lovable shoujo "doki doki" moment. I have many testimonies of people squealing in happiness when Kazehaya and Sawako finally get a major romance development, like a confession. This is the charm of KnT. It's slow, but it's undeniable sweet - so sweet that you get to fall in love with the characters and you get sucked up into the moment. If you are willing to stick to the slow romance, KnT is a big, big enjoyable story.

So while it's slow, if you stick to it, you get major enjoyment along with it. So you get a 4 in the enjoyment section, KnT!

Overall

KnT is not for everybody that is all I can say. If you are not a fan of the sweet, slow shoujos, steer away from KnT. Don't try to read it, because it will get you frustrated (something like: "Why doesn't Sawako get it?! He LIKES you, Sawako, arrgh!" might happen).
But if you are willing to stick to the slowness and enjoy sweet fluff of the ride, KnT will be come out to be a very big treat.

Overall - 8.8 stars out of 10
Wow. Long reviews are long.