I was really excited about playing this game, until it ended.
Ico is a beautiful game, but is just too linear. There isn't very much action, but there really isn't supposed to be. I found the answers to the puzzles to be very obvious and only found myself frustrated with what to do once.
I beat the game in just over 6 hours and much to my dismay, that unlocked nothing, there was no extra incentive for me to play it again. I did enjoy those 6 hours and saving Yorda and Ico was quite rewarding. The world of Ico is a beautiful and expansive one (even though it takes place entirely in one castle.) and some might get more challenge out of it than I did.
If you see this game on sale for cheap, and you haven't played it, get it. Otherwise, it'd be a great rental.