This review does NOT contain storyline spoilers of any kind.
Due to the fact that Clannad was a visual novel at heart, these "alternate world" OVAs came out. I'm kinda divided. I played the VN after I watched the anime and I feel that both Kyou and Tomoyo deserve more. But then, I watched the OVA again and I've finally settled down to a conclusion: they're good.
They managed to compress a beautiful story (albeit, a side story) into 24 minutes of pure masterpiece. All the characteristics of the original Clannad are there: the real emotions, the romantic development, the anger, the sorrow, it's all there.
If you enjoyed Clannad and After Story do watch these OVAs as well.