I strongly suspect that Honey and Clover creator Umino Chika, while on her way to deliver character designs for Eden of the East, decided to “spice up” the lives of the members of Production IG. How else can I explain how good Kimi ni Todoke has been?
Not to take anything away from the original creator of Kimi ni Todoke, Shiina Karuho, seeing as it’s her strong story and nice character designs that they’re working with, and certainly Production IG has always been known for its high standards of animation quality, but KnT is a beast unlike any other unleashed by the Igg (that’s how the cool people pronounce it, you know). Rather than using their expertise to make a more fleshed out and realistic-looking show, as one might expect from the studio that brought us Ghost in the Shell: SAC, what Production IG has managed to achieve is a show that truly looks shoujo in a way most anime have not, including perfectly good works such as Cardcaptor Sakura and Itazura na Kiss.
There’s a very strong understanding by the staff on this show as to when to utilize the more visually two-dimensional and emotional elements and when to incorporate a three-dimensional sense of spacing among the characters, and it, and the result is that it achieves that pastel and wispy shoujo manga feel while still making sense as an animation. In a way it reminds me of 70s-style shoujo, only with less emphasis on the melodramatic, and more technical skill on the part of the animators.
And even if you don’t care about all of that stuff I just said, note that Kimi ni Todoke is still very good, and does a good job of murdering cliches with an 80 lb. battle axe, which I will assure you is the perfect metaphor for this show. Good shoujo, from Igg to you.