The music of Ico, like Shadow of the Colossus, has a very unique style to it... More of a dramatic folklike style than anything else. Michiru mananged to catch the mood of each scene of the game where this is played perfectly.
The only initial problem I have with it is the mere oddness of each piece, and the shortness of it. While there is an upside to the shortness of each piece, it being that the song isn't played throughout the whole game, rather, is used in places in order to catch the mood, I like longer pieces. The oddness that I speak of is the fact that for the most part, there is no clear tune, like on Coffin and track 12 Deja Vu. However, pieces like Heal, Castle in the Mist, and You Were There catch the imagination, and are absolutely beautiful pieces.
My favorite song of the bunch is You Were There; it is a beautiful and inspiring tune, and the overall flow of it is smooth. The vocal is the sweet voice of a child, and I imagine Ico singing the piece. However, the exact words to the vocal aren't clear in pronounciation.
Overall, I give this an 8/10. A very good soundtrack for those who love folk and celtic music.