The world of Shadow of the Colossus is rich and detailed, but drably colored. Everything looks undeniably lush and exotic, but the poor PlayStation 2 is crushed under the weight of the math required to draw these landscapes and animate these gigantic colossi around it. As a result, the scenery often pops abruptly into existence, and nothing moves remotely as smoothly as it should, even if the movements themselves are artistically beautiful.
While we're complaining, we should also mention that both the camera and Agro's controls fight the player as much as the colossi. On horseback, rather than just pointing the analog stick in the direction you want Agro to go, you press up to go forward and left or right to pivot. It can get tricky when the camera is moving around; and the camera is always moving. It wants to be cinematic and artistic, even if that means giving you a poor view of what's going on. You should plan on repositioning it constantly.