My opinion ?
Story: Everything is explained very well but you should also Watch http://myanimelist.net/anime/4181/Clannad:_After_Story (not all has been explained in First series)
Art: Very well maded/
Sound: it impossible to put better sound. its not Just a sound, every OST has emotions, or how should i say?
Characters: every each character is oryginal in self-beining
Enjoymemnt: couldn't be better. i even cried in some moments
