This is Ghibli the way I like it best, sans weird fantasy monsters (I'm looking at you, Ponyo), and heavy on the historical slice-of-life, which always rates high in my book.
Story: I liked the story. I've seen some complaining that the drama wasn't dramatic. I guess if you're over-focusing on the romantic drama, that's true. "OMG we're siblings but we're in love?! Ooops, just a misunderstanding," is admittedly not anything revolutionary, however, I would argue that because Shun's adoption occurred on account of historical events, it's not as fluffy as it would seem. Remember how the adults talk about his sort of situation occurring with some frequency? Beyond that, what really kept me going was the save the clubhouse plot, mostly because the animation sequences that took place inside the clubhouse were so rich and different.
Animation: This is a Ghibli film; do we even need to discuss this topic?
Sound: See above + historical songs.
Characters: The main characters were pretty typically Ghibli. I was intrigued by the side characters, especially the grandmother, artist, and the lady doctor. Shun's father was also fairly atypical. Solid characters, interesting enough to drive the plot.
All in all, this movie is typical Ghibli. But that doesn't make it any less enjoyable or well done!