I watched the the first series, Clannad, and found some lack of enjoyment, however, i took the risk and watched AS. I am glad that i did. Clannad moved me in many ways. There were moments i laughed, there were moments i am disappointed on characters decisions and there were moments i cried.
From all the anime's or manga's i read(some of them i cant remember, so they are not in my list) Clannad and AS showed me a different view of life. Even though i only watch the whole series within a week, it feels like i have been living through Clannad for years. I definitely recommend anyone to watch this.