Each girl in Clannad (main and supporting cast) has her own personality quirk, one of which is bound to attract a fan. That kind of variety works to attract many viewers. But Clannad is not necessarily a "harem" by its general definition. While Tomoya's daily life is indeed surrounded by beautiful girls, he is not interested in dating any of them. Instead, he becomes involved (accidentally or not) in their hopes and concerns, and the storytelling of the series becomes apparent through the dramatic character development.
In most episodes, the flow of the story involves each girl a little bit at a time, which I prefer since the drama feels more realistic. Character development occurs in parallel, and more drama can be drawn from the intertwining relationships among the characters. Some episodes do define their focus on a particular girl, but the overall immersive feel of the series is not lost.
The fact that Kyoto Animation produces this series has been a recent guarantee that the artwork is superb. Characters and backgrounds are brilliantly drawn. Motion of all kinds are captured smoothly -- not only characters walking but also the wind blowing on their clothes. Body language is also visible, which speaks louder than words most times.
All the music is taken from the original game, which many fans praise, although it does not allow for too much creativity. Regardless, the original music is full of variety and is easy on the ears. Plus it was composed to fit the story for a reason; why not reuse it? The ED thing (at least the lyrics) is new, though, I believe.
While the storytelling is excellent, most of the enjoyment lies in the humor, which is mostly cute and/or slapstick stuff. Only in rare occasions does the humor detract from the story and drama, but it is mostly timed well and presented as a fun change of pace after a very emotional sequence (or before the next one). Speaking of emotional sequences, I found myself crying on more than one occasion. Clannad pulls at the heartstrings very effectively when the time is right.
Overall, the defining points of Clannad are the supernatural elements (gotta break the laws of physics a tiny bit to tell a unique story), the moe factor (cute girls are cute, but not totally unrealistic), and the emotionally gripping story (everyone is connected to the overall theme of the series -- family).
I regret that the series is about to end, but I have loved it every step of the way. Kyoto Animation has such amazing respect right now that I'll give all of its future Key adaptations a 10/10, before having seen any of the episodes or knowing anything about the series. They know how not to disappoint.
(Originally written 11/22/07 after episode 7. Last updated 02/09/08 after episode 17.)
